{-
n! means n x (n - 1) x ... x 3 x 2 x 1.
For example, 10! = 10 x 9 x ... x 3 x 2 x 1 = 3628800,
  and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.
Find the sum of the digits in the number 100!.
-}

import           Data.Char (digitToInt)

read' :: Integer -> String
read' = show

main :: IO ()
main = do
  print $ "Answer: " <> show ans

ans :: Int
ans = sum $ map digitToInt $ read' $ product [1..100]