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import SumNatsVect (sumNats)
-- Solution for 1st Euler problem
-- Add all the natural numbers below 1000 that are multiples of 3 or 5.
solutionLists maxN
= let sumOnetoN n = n * (n+1) `div` 2
sumStep s n = s * sumOnetoN (n `div` s)
in sumStep 3 (maxN - 1) + sumStep 5 (maxN - 1) - sumStep 15 (maxN - 1)
solutionLists2 maxN
= sum [ x | x <- [0.. maxN - 1]
, (x `mod` 3 == 0) || (x `mod` 5 == 0) ]
main
= do let n = 1000
print $ solutionLists n
print $ solutionLists2 n
print $ sumNats n
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