-- Instead of this
-- sumMultiples3or5 s = sum [x | x <- [3..s-1], x `mod` 3 == 0 || x
`mod` 5 == 0]
-- Isn't this faster
sumMultiples3or5 s = sum ([x | x <- [3,6..s-1]] `merge` [x | x <-
[5,10..s-1]])
merge xs [] = xs
merge [] ys = ys
merge txs@(x:xs) tys@(y:ys)
| x < y = x : xs `merge` tys
| x > y = y : txs `merge` ys
| otherwise = x : xs `merge` ys
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