import Data.Char

-- Funcao que valida o numero fornecido
checkDigit :: [Int] -> Bool
checkDigit =
     let -- validar code.
     code = take 12 intCode
     expr1 = ( sum $ zipWith (*) code [1,3,1,3,1,3,1,3,1,3,1,3])
   -- validar ultimo digito codebar é somatorio da multiplicacao dos num por 1,3,1,3,... no caso 12 numeros
     d = ((expr1 div 10) +1)*10  -- problema aqui
     v_code = d - expr1
     in v_code == intCode !! 12

main = do

  let code = "7895144059013"
      intCode = (map digitToInt code)
      result = checkDigit intCode
  putStrLn ( show result)