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: Wrong Answer)

import Data.Char (toLower)

main = do
    [_,k] <- map read . words <$> getLine
    s <- getLine
    print $ solve s 1 k

solve :: String -> Int -> Int -> String
solve (c:cs) i k
  | i == k    = toLower c : cs
  | otherwise = c : solve cs (i+1) k