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 PHP (7.4.4) (judge verdict: Runtime Error)

<?php
  fscanf(STDIN, "%d %d", $n, $k);
  fscanf(STDIN, "%s", $s);

  $cp = substr($s, $k-1,1);
  $sstr = strtolower($cp);

  echo substr_replace(&s, $sstr, $k-1, 1);