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All right guys, it's time to show what you're made of.

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Here's another code challenge. And this one is again,

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another difficult challenge and the arms really show you just how difficult it

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is, but you're going to flex and you're going to get stronger.

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And it's only through struggle that you're going to become a better coder.

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So in this code exercise, we're going to build a love calculator.

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And the way that it's going to work is the same method that I used when I was

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10, pretty much.

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And I really recommend reading up on this particular Buzzfeed article,

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which is of course, very reputable

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and it's going to tell you exactly how this program is going to work.

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So once you've managed to scroll past all the GIFs, it will tell you, um,

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the method. So you write your name, his or her name,

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and then the words true and love. Now,

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then you are going to count the number of times T-R-U-E occur in both of

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your names. And then you're going to count the number of times,

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L-O-V-E occur in both of your names. Once you've got those numbers,

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so here T-R-U-E adds up to six, L-O-V-E adds up to three.

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Then you'll get the percentage that you are compatible with this other person.

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So not only did you get to learn Programming on this course,

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you also get the discover your destiny.

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The idea is that we're going to convert this very time-consuming process into a

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computer program. So once you've understood how it works,

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you're going to write the code for it. Now,

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in order to be able to calculate the love score,

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there's two important things that you should read in the hint.

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One is you will need to use the lower function, and all that this does is it

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takes a string, let's say we've got the string Angela.

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And notice how that first letter is a capital A.

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If I write .lower parentheses,

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then it will reduce all of the capital letters to lowercase letters.

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And if you were wondering how you would've known to use this,

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then you can head over to the Stack of flow question

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in which somebody asks exactly this question, how do you turn something

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that's uppercase into a lowercase character in Python.

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The second function you'll need is the count function.

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And this will give you the number of times a letter occurs in a string,

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which is super useful when it comes to this particular challenge. So again,

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let's use our string, Angela, and then I'm going to write count.

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And then in between the parentheses,

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I'm going to specify what it is that I want to count.

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So let's say I want to count the character A inside this string,

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and I hit enter. It comes up with one,

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even though you can see there's actually two A's in the string, in my name,

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it only counts one lowercase a. So that's why this first step was super,

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super useful.

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So let's say lower_case_name equals, um,

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Angela.lower. And then,

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um,

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let's go ahead and do lower_case_name.count,

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and then we're going to count for a again. Now you'll see it gives us two,

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because we were able to convert everything to lowercase,

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and then use the count function to check the number of times the character a

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occurs in this string. And again, I've linked to a Stack Overflow question

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which is how you might've found out to use this count function and how you might

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use it in terms of code examples. Now,

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there's a second step to this challenge

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because not only do we want to know the love score,

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we also want to give the user an interpretation.

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So the interpretation is here. For love scores that are less than 10 or greater

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than 90, the message is going to say "Your score is X." And of course,

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replace that X with the actual score. You go together like Coke and Mentos.

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Now, if their love score was between 40 and 50,

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the message is going to read your score is, whatever it may be,

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you are all right together. And finally,

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for all other scores, the message is just going to give them their score.

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Your score is XYZ. In this case, there's two inputs,

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somebody's name, and then somebody else's name.

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And then you're going to check for the number of times T-R-U-E occurs in

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both of those names, L-O-V-E occurs in those names,

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then you going to combine these digits together to get a love score.

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Pause the video now, have a look at everything that's in the instructions,

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read it all and then go ahead and give that a go.

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[inaudible]

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All right. So the first step is to work out the love score, right?

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So we need to figure out how many times each of these letters occur in these

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names.

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The first thing that we need to do is to combine the names,

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because we're looking for the number of times,

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let's say a T occurs in these names and we're treating them as one string,

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right? So I don't wanna check it separately and then have to add it together.

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So let's call it a combined_string and lets set that to equal name1 + name2.

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And this is just going to concatenate those two strings together

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so we'll be able to check them only once. It makes it more efficient,

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right? The next step is to guard against cases

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where the user is inputting their name like this, which many people do,

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or they might even write it like this.

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So we have to turn everything into lowercase.

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So let's call it a lower_case_string

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and that will be combined_string. lower just as I demoed previously using

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this lower function. So now we've got everything in lower case,

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we're going to start checking for this first word,

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T-R-U-E. So let's first check

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how many times the letter T occurs in this lowercase string of both people's

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names.

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So we can say lower_case_string.count

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and then inside the parentheses, we specify the string we're looking for

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which is 't' and then I'm going to save this to a variable

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which I'll just call 't' again. And then we're going to repeat this several times,

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hopefully for practice sake, you'll type it all out. But in my case,

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I'm just going to copy and paste it, which is usually error-prone,

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but we'll try to be careful.

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So now that we've got the number of times 't' occurs, 'r' 

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occurs, 'u' and 'e' occurs, we can now add it all up.

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So let's say true = t + r + u + e.

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So now we've got the first digit of our love score and we have to go ahead and

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do the same thing for L-O-V-E. So again, for time sake,

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I'm just going to copy that and then go ahead and change this to l,

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o, v, e and l, o, v, e.

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And then I'm going to go ahead and calculate the total for that

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which is going to be l + o + v + e.

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And now I've got both of these numbers and I'm going to try and concatenate them

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together to achieve this two-digit number.

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To do that, I'm going to create a love score variable

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that's going to keep hold of this.

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And then I'm going to say true + love.

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And remember that at this stage, both true and love are actually integers.

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That's how we were able to add them together.

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So if I want to turn them into a string in order to be able to concatenate them

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together, I have to convert them to strings.

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The final thing we have to do is just to go ahead and print this love score.

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So we're not going to print anything else for now.

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Let's just go ahead and test it out. So let's run our code

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and let's type my name and then

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their name, Jack Bauer, of course. And then it gives us the score.

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So five, three.

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So that means everything so far has pretty much worked.

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So now all we have to do is use our knowledge of if statements to give a

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corresponding interpretation or a message.

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If the score is less than 10 or greater than 90,

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so if love_score is less than 10 or love_score is greater than 90,

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so we're using that logical or operator here to check if either this condition

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or this condition is true. And if you find it helpful,

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which I usually do,

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it's easy to wrap these conditions in their own set of parentheses.

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Now, Python doesn't actually care. Either method works.

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But for us humans, this is a little bit more readable.

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So under this condition,

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what we're going to print out is

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Your love score is,

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and then we'll insert the love_score variable here,

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and we're going to of course be using f-strings, so let's add that.

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And then we're going to write you go together like Coke and Mentos.

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So that's our first condition done. Now,

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the next condition is what if their love score is between 40 and 50.

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So let's go ahead and add an elif here.

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Elif

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the love_score is greater than or equal to 40

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and the love_score is less than or equal to 50,

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so that catches the cases where the love score is between 40 and 50.

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So both of these conditions must be true for this statement to fire.

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And in this case,

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what we want to do is we want to print out this sentence.

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So your score is,

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let's just insert the love_score in here.

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[inaudible]

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Your score is this particular love score. You are alright together.

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Now the final thing we said is if it doesn't match any of these conditions,

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then the message is just going to be their score.

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So that means we can catch everything else using an else statement

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and we can simply just print "Your score

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is this particular number."

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Now at this stage, you might think you're done, but if you actually run it,

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you're going to get an error. So let's go ahead and test it with the same names

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as before.

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You can see that we get a type error on line 27,

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and it says that the comparison less than is not supported between instances

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of string and int.

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So the problem here is that in order to concatenate these two numbers,

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we had to turn them into strings.

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So that let's say that this number was equal to five and this number was equal

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to six. Then instead of getting 11, which is not what we want,

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we actually get 56 'cause they're both strings and these strings get concatenated

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together.

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But the problem occurs on the next step because we wanna compare the love score

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against an actual number, then if it's a string,

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it's not going to work. So in order to solve this,

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then we actually have to convert the love score into an integer.

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So you could use a separate step.

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So the int_score equals int

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and then we wrap it around the love score. Alternatively, um,

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and a lot easier is to simply just wrap that whole line inside a set of brackets

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and convert the whole thing into an integer on the same line.

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It depends on how comfortable you are with this code as to which option you'll

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choose. Now that we're done here,

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let's go ahead and run our code again and let's just check it out.

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Your score is 42. You are all right together.

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So now our code seems to be working and we've now completed this code challenge.

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How did you get on with this challenge?

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Did you manage to get everything right?

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Did you get stuck at certain places?

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Have a think about which parts of this challenge were the hardest and see if you

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can review some of those concepts so that the next time you encounter them,

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you'll be able to tackle them with confidence.