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: Wrong Answer)

import re

a,b = list(map(int, input().split()))
c = input(" ")
if c not in "A,B,C":
    exit()
if c in "A,B,C":
    d = re.compile(c[b-1])
    e = d.sub(c[b-1].lower(), c)
    print(e)