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 Python (3.4.3) (judge verdict: Accepted)

# -*- coding: utf-8 -*-
def main():
    answer = ''
    N,K = map(int,input().split())
    S = list(input())
    if S[K-1] == 'A':
        S[K-1] = 'a'
    elif S[K-1] == 'B':
        S[K-1] = 'b'
    elif S[K-1] == 'C':
        S[K-1] = 'c'
    for s in S:
        answer += s
    print(answer)

if __name__ == '__main__':
    main()