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 (Clang 3.8.0) (judge verdict: Accepted)

#include <stdio.h>

int main() {
  int n, k;
  scanf("%d %d", &n, &k);
  for (int i = 0; i < n + 1; i++) {
    char tp = getchar();
    if (i == k) {
      char tpx = tp - (-'a' + 'A');
      putchar(tpx);
    } else {
      putchar(tp);
    }
  }
  printf("\n");

  return 0;
}