If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.

In scala, adding to a variable isn't good form, the proper way to brute force through every value in a range is to use recursion. And to keep from blowing the stack, I make sure it's tail recursive.

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In [13]:
```@annotation.tailrec
final def natural3and5brute(upper:Int = 1000, current:Int = 1, output:Int = 0):Int = {
if (current == upper) output
else {
val newout:Int = if (current % 3 == 0 | current % 5 == 0) output + current else output
natural3and5brute(upper, current + 1, newout)
}
}

```
```

```
In [14]:
```natural3and5brute()

```
```

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In [ ]:
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