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]){
    $result .= mb_strtolower($char[$i]);
  }
  $result = $result.$char[$i];
}
 
echo $result;
 
?>