{-

- Solution to Project Euler problem 130

- Copyright (c) Project Nayuki. All rights reserved.

-

- https://www.nayuki.io/page/project-euler-solutions

- https://github.com/nayuki/Project-Euler-solutions

-}

import qualified EulerLib

main = putStrLn (show ans)

cond i = (mod i 5 /= 0) && (not (EulerLib.isPrime i)) && mod (i - 1) (findLeastDivisibleRepunit i) == 0

ans = sum (take 25 (filter cond [7,9..]))

findLeastDivisibleRepunit :: Integer -> Integer

findLeastDivisibleRepunit n = if (mod n 2) == 0 || (mod n 5) == 0

then 0

else let

func 0 _ k = k

func s p k = func (mod (s + p * 10) n) (mod (p * 10) n) (k + 1)

in func 1 1 1