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 (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <ctype.h>

int main(void)
{
  int i,N,K;
  scanf("%d %d",&N,&K);
  char a[N],b[N];
  scanf("%s",a);

  for(i = 0;i < N;i++) {
    b[i] = ' ';
    if(i + 1 == K) b[i] = tolower(a[i]);
    else b[i] = a[i];
    printf("%c",b[i]);
  }  

  printf("\n");
  return 0;
}