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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php

  list($n, $m) = explode(" ", trim(fgets(STDIN)));

  list($s) = explode(" ", trim(fgets(STDIN)));

  $m--;
  for ($i=0; $i<$n; $i++) {
    if($i==$m){
      if($s[$i]=='A'){
        echo 'a';
      }else if($s[$i]=='B'){
        echo 'b';
      }else{
        echo 'c';
      }
    }else{    
      echo $s[$i];
    }
  }