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)

def resolve():
    N, K = map(int, input().split())
    S = input()
    S_ = []
    for i in range(N):
        a = S[i]
        if i != K - 1:
            S_.append(a)
        else:
            S_.append(a.lower())

    S_ = ''.join(S_)
    print(S_)

resolve()