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)

n,k=map(int,input().split())
s=input()
ls=[c for c in s]
for i in range(n):
    if i==k and s[i]=='A':
        ls[i]='a'
    elif i==k and s[i]=='B':
        ls[i]='b'
    elif i==k and s[i]=='C':
        ls[i]='c'
ss = ''.join(ls)
print(ss)