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 C++14 (GCC 5.4.1) (judge verdict: Runtime Error)

#include <bits/stdc++.h>
using namespace std;

int main(){
  int N,B;
  cin >> N >> B;
  string S;
  if (S.at(B) == 'A') {
    S.at(B) = 'a';
    cout << S << endl;
  } else if (S.at(B) == 'B') {
    S.at(B) = 'b';
    cout << S << endl;
  } else if (S.at(B) == 'C') {
    S.at(B) = 'c';
    cout << S << endl;
  }
}