content: digits :: String
  digits = "\
  \73167176531330624919225119674426574742355349194934\
  \96983520312774506326239578318016984801869478851843\
  \85861560789112949495459501737958331952853208805511\
  \12540698747158523863050715693290963295227443043557\
  \66896648950445244523161731856403098711121722383113\
  \62229893423380308135336276614282806444486645238749\
  \30358907296290491560440772390713810515859307960866\
  \70172427121883998797908792274921901699720888093776\
  \65727333001053367881220235421809751254540594752243\
  \52584907711670556013604839586446706324415722155397\
  \53697817977846174064955149290862569321978468622482\
  \83972241375657056057490261407972968652414535100474\
  \82166370484403199890008895243450658541227588666881\
  \16427171479924442928230863465674813919123162824586\
  \17866458359124566529476545682848912883142607690042\
  \24219022671055626321111109370544217506941658960408\
  \07198403850962455444362981230987879927244284909188\
  \84580156166097919133875499200524063689912560717606\
  \05886116467109405077541002256983155200055935729725\
  \71636269561882670428252483600823257530420752963450"
  
  parseChar :: Char -> Int
  parseChar c =
      fromEnum c - fromEnum '0'
  
  slice :: Int -> Int -> [a] -> [a]
  slice from count xs = take count $ drop from $ xs
  
  subsequencesOfLength :: Int -> [a] -> [[a]]
  subsequencesOfLength n xs =
      map (\index -> slice index n xs) [0 .. len - n]
      where len = length xs
  
  productOfString :: String -> Int
  productOfString s =
      product $ map (parseChar) s
  
  maximumSequenceProduct :: Int -> String -> Int
  maximumSequenceProduct seqlen str =
      maximum $ map productOfString $ subsequencesOfLength seqlen str
  
  main :: IO ()
  main = print $ maximumSequenceProduct 13 digits
  