# nayuki/Project-Euler-solutions

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 {- - Solution to Project Euler problem 160 - Copyright (c) Project Nayuki. All rights reserved. - - https://www.nayuki.io/page/project-euler-solutions - https://github.com/nayuki/Project-Euler-solutions -} main = putStrLn (show ans) ans = f (10^12 :: Integer) -- factorialSuffix f n = md \$ (g n) * (powMod 2 ((c 2 n) - (c 5 n))) -- factorialish g n = md \$ (ge n) * (go n) -- evenFactorialish ge 0 = 1 ge n = g (div n 2) -- oddFactorialish go 0 = 1 go n = md \$ (go (div n 5)) * (h n) -- factorialCoprime h n = foldl (\x y -> md \$ x * y) 1 [k | k <- [1..md n], (mod k 2) /= 0 && (mod k 5) /= 0] -- countFactors c n 0 = 0 c n m = (div m n) + (c n (div m n)) -- Modular arithmetic powMod _ 0 = md 1 powMod x y | mod y 2 == 0 = temp | otherwise = md (temp * x) where temp = powMod (md (x * x)) (div y 2) md n = mod n (10^5) -- Modulo reduction for this problem