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)

n, k = map(int, input().split())
listS = list(input())
if k == 0:
    print(listS[0].lower()+"".join(listS[1:]))
elif k == n:
    print("".join(listS[:n-1])+listS[n-1].lower())
else:
    print("".join(listS[:k-1])+listS[k-1].lower()+"".join(listS[k:]))