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 = (int(i) for i in input().split())

S = input()

if S[K - 1] == "A":
    S = S[:K-1]+"a"+S[K:]
if S[K - 1] == "B":
    S = S[:K-1] + "b" + S[K:]
if S[K - 1] == "C":
    S = S[:K-1]+"c"+S[K:]

print(S)