Ошибка Program error: Prelude.read: no parse

(1022 reductions, 1633 cells)
Main> :main
ENCODE =>
Input the string for encoding: "hello"
Input keys a and b: 1 2
 
This is an encoded string => 
Program error: Prelude.read: no parse

module Main where
import IO
import Data.Char
import Data.Maybe
import Data.List
import qualified Data.Set as Set
 
main = do 
       hSetBuffering stdout NoBuffering
       putStrLn "ENCODE =>"
       putStr "Input the string for encoding: "
       s<- getLine
       putStr "Input keys a and b: "
       a<- getLine
       b<- getLine
       let x= (read a):: Int
       let y= (read b):: Int 
       putStr "This is an encoded string => "    
       print $ encode x y s
 
 
let2int :: Char -> Int
let2int c | isLower c = ord c - ord 'a'
          | otherwise = let2int (toLower c)
 
int2let :: Int -> Char
int2let n = chr (ord 'a' + n)
 
shift :: Char -> Int -> Int -> Char
shift c a b | isLetter c = int2let ((x * a + b) `mod` 26)
            | otherwise = c
            where x = let2int c
 
isCoprime :: Int -> Int -> Bool
isCoprime a b = gcd a b == 1
 
valid_param :: Int -> Bool
valid_param a = isCoprime a 26
 
encode :: Int -> Int -> String -> Maybe String
encode a b xs | valid_param a = Just [shift x a b | x <- xs]
              | otherwise = Nothing

(1022 reductions, 1633 cells)
Main> :main
ENCODE =>
Input the string for encoding: "hello"
Input keys a and b: 1 
2

       putStr "Input the string for encoding: "
       s<- getLine
       putStr "Input keys a and b: "
       ~[x,y]<- (map read . words) <$> getLine
       putStr "This is an encoded string => "    
       print $ encode x y s

module Main where
import IO
import Data.Char
import Data.Maybe
import Data.List
import qualified Data.Set as Set
 
main = do 
       hSetBuffering stdout NoBuffering
       putStrLn "ENCODE =>"
       putStr "Input the string for encoding: "
       s<- getLine
       putStr "Input keys a and b: "
       ~[x,y]<- (map read . words) <$> getLine
       putStr "This is an encoded string => "    
       print $ encode x y s
 
let2int :: Char -> Int
let2int c | isLower c = ord c - ord 'a'
          | otherwise = let2int (toLower c)
 
int2let :: Int -> Char
int2let n = chr (ord 'a' + n)
 
shift :: Char -> Int -> Int -> Char
shift c a b | isLetter c = int2let ((x * a + b) `mod` 26)
            | otherwise = c
            where x = let2int c
 
isCoprime :: Int -> Int -> Bool
isCoprime a b = gcd a b == 1
 
valid_param :: Int -> Bool
valid_param a = isCoprime a 26
 
encode :: Int -> Int -> String -> Maybe String
encode a b xs | valid_param a = Just [shift x a b | x <- xs]
              | otherwise = Nothing

() :: IO ()
(1378947 reductions, 1797594 cells, 9 garbage collections)
Main> :main
Reading file "C:\Users\Admin\Desktop\test22.txt":
Parsing........................................................................
Dependency analysis
ERROR file:.\test22.txt:8 - Undefined variable "<$>"
Data.Set>