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.Char

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

solve _ _ [] = []
solve k i (c:s)
  | k==i = toLower c:solve k (i+1)  s
  | otherwise = c:solve k (i+1) s