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>
int main(void){
  char s[50],sc[50];
  int sa,n,k;
  scanf("%d %d",&n,&k);
  scanf("%s",s);
  sa='A'-'a';
  for(int i=0;i<n;i++){
    if(i==k-1){
      sc[i]=s[i]-sa;
    }
    else{
      sc[i]=s[i];
    }
  }
  sc[n]='\0';
  printf("%s",sc);
}