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 PyPy3 (7.3.0) (judge verdict: Wrong Answer)

def INT():
    return int(input())

def MI():
    return map(int, input().split())

def LI():
    return list(map(int, input().split()))

N, K = MI()
S = input()
S_lower = S.lower()
S = S.replace(S[K - 1], S_lower[K - 1], 1)

print(S)