How to fix parse error on input 'else' for Haskell code

For the following code, I am getting a parse error on input 'else' for line 33 (the third 'else' in the code) when I try to compile. How can I fix this?

import Control.Monad
import System.Directory
import System.IO
import System.FilePath.Posix (takeDirectory)
import System.Environment

main :: IO ()
main =  do

let loop = do
    let cmd = 'x'
    -- take directory name --
    print "Enter Directory Name "
    dir <- getLine
    -- check whether directory exist or not
    check <- doesDirectoryExist dir
    if check == True
        then do
            ipt <- getLine -- take command
            let cmd = take 1 ipt
            if cmd == "l"
                then do 
                    contents <- listDirectory dir
                    print contents
                else
                    if cmd == "r"
                        then do
                            let index = drop 1 ipt
                        else
                            if cmd == "a"
                                then
                                    let info = drop 1 ipt
                                else 
                                    putStrLn (cmd ++ "Invalid Command")
        else putStrLn "Directory not Exist"
    when ( cmd /= 'x' ) loop --  if command equals to x end the loop

loop