-- An irrational decimal fraction is created by concatenating the positive
-- integers:
--
-- 0.123456789101112131415161718192021...
--
-- It can be seen that the 12th digit of the fractional part is 1.
--
-- If d[n] represents the nth digit of the fractional part, find the value of
-- the following expression.
--
-- d[1] × d[10] × d[100] × d[1000] × d[10000] × d[100000] × d[1000000]

import Euler

nthDigit = go 1
   where
      go m n = if n < m*10^m
               then toDigits (n `div` m) !! (n `mod` m)
               else go (m + 1) (n + 10^m)

main = print $ product $ map (nthDigit . (10^)) [0..6]