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 (2.4.0) (judge verdict: Accepted)

def slove():
    import sys
    input = sys.stdin.readline
    n, k = list(map(int, input().rstrip('\n').split()))
    s = str(input().rstrip('\n'))
    a = []
    for i in range(n):
        if i == k - 1:
            a.append(s[i].lower())
        else:
            a.append(s[i])
    print("".join(a))


if __name__ == '__main__':
    slove()