Project Euler Problem 033

import Data.Ratio
import Data.List
n :: [Integer]
n = [1..9] --0はtrivialになるので除いた
lis :: [(Integer, Integer)]
lis = nub $ sort [(num,den) | a<-n,b<-n,a/=b,d<-n,d/=b,
                  let num = 10*a+b,
                  let den = 10*b+d,
                  (num%den) == (a%d)
                            ]
ans1 :: Integer
ans1 = denominator $ product $ map (\(l,r)->l%r) lis
-- 100
main :: IO ()
main = print ans1