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
fscanf(STDIN, '%d %d', $length, $key);
fscanf(STDIN, '%s', $str);
$ans = '';
for ($i=0; $i < $length; $i++) { 
    if ($i + 1 === $key) {
        $ans .= strtolower($str[$i]);
    } else {
        $ans .= $str[$i];
    }
}
echo "$ans\n";