project euler p-104, why did this program eat up all my memory space?

gistfile1.hs

import Data.Char
import Data.List

fibSeq :: [(Integer, Integer)]
fibSeq = map (\(n, (a,_)) -> (n, a)) $ iterate (\(n, (a,b))->(n+1, (b,a+b))) (1,(1,1))

fstPandigital :: Integer -> Bool
fstPandigital n = charNum == "123456789" where
	charNum = sort $ take 9 $ show n

lstPandigital :: Integer -> Bool
lstPandigital n = charNum == "123456789" where
	charNum = sort $ show $ n `mod` 1000000000

result = fst $ head $ filter (\(n, x)-> (lstPandigital x) && (fstPandigital x) ) fibSeq

main = print result

you MUST compile this program using optimization, or your memory space will be eaten up...