Problem:
Score : 100 points

Problem Statement

You are given a string S of length N consisting of A, B and C, and an integer K which is between 1 and N (inclusive).
Print the string S after lowercasing the K-th character in it.

Constraints

1 ≤ N ≤ 50

1 ≤ K ≤ N

S is a string of length N consisting of A, B and C.

Input

Input is given from Standard Input in the following format:

N K
S

Output

Print the string S after lowercasing the K-th character in it.

Sample Input 1

3 1
ABC

Sample Output 1

aBC

Sample Input 2

4 3
CABA

Sample Output 2

CAbA

Solution in Haskell (GHC 7.10.3) (judge verdict: Accepted)

import Data.List (sort)
import Data.Char (toLower)

readIntLine :: IO ([Int])
readIntLine = do
    x <- getLine
    return $ map (read :: String -> Int) $ words x

main :: IO ()
main = do
    [n,k] <- readIntLine
    s <- getLine
    putStrLn $ lowered s k

lowered :: String -> Int -> String
lowered s k =
    let p1 = take (k-1) s
        p2 = toLower $ head $ drop (k-1) s
        p3 = drop k s
      in p1 ++ [p2] ++ p3