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: Wrong Answer)

<?php
  $int = explode(" ",trim(fgets(STDIN)));
  $char = str_split(trim(fgets(STDIN)));
  $result;
  for($i=0;$i<$int[0];$i++){
    if($i === $int[1]){
      $result = $result.$char[i];
    }
    $result = $result.$char[i];
  }

  echo $result;
?>