euler008.hs

digits :: Integer -> [Integer]
digits 0 = [] 
digits n = n `mod` 10 : digits (n `div` 10)

split :: Integer -> [Integer] -> [Integer]
split 0 _ = []
split n (x:l) = x : split (n - 1) l

number = 7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450

chnks :: Int -> [Integer] -> [[Integer]]
chnks _ [] = []
chnks s (x:l) = fst (splitAt s (x:l)) : chnks s l
-- chnks (x:l) = split 13 (x:l) : chnks l

solve :: Int -> Integer
solve n = maximum (map (\l -> foldl (*) 1 l) (chnks n (digits number)))


main = do
    print(solve 13)