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: Accepted)

#include <iostream>
#include <string>
#include <algorithm>
#include <cctype>
#include <cstdio>
// #include <cstdio>
// #include <bitset>
// #include <math.h>
//#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a; i<b; i++)

const int MAX_N = 50;
int n, k;
string S;

int main() {
  scanf("%d %d", &n, &k);
  cin >> S;

  // printf("%d %d\n", n, k);
  // cout << S << "\n";
  //
  // printf("%c\n", tolower('a'));
  // printf("%c\n", tolower('A'));
  // printf("%c\n", tolower('!'));
  int cnt = 1;
  for(auto tmp_c: S) {
    if (cnt==k) {
      printf("%c", tolower(tmp_c));
    } else {
      printf("%c", tmp_c);
    }
    cnt++;
  }
  printf("\n");

  return 0;
}