Problem 1

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.

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sum[n | n <- [1..999], (mod n 5 == 0) || (mod n 3 == 0)]

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