-- Find the sum of the only eleven primes that are both truncatable from left
-- to right and right to left.

import Euler
import Data.Array.Unboxed

truncations n = map fromDigits $ filter (not . null) $ inits (toDigits n) ++ tails (toDigits n)

isPrimeArr = isPrimeArray 1000000
isPrime n  = n >= 2 && isPrimeArr!n /= 0

main = print $ sum $ take 11 $ filter (all isPrime . truncations) [11..]