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 (5.6.30) (judge verdict: Wrong Answer)

<?php
$pointsN = trim(fgets(STDIN));
$arrN = explode(" ", $pointsN);  //半角スペース区切りの要素を格納
$a1 = (int)($arrN[0]/100);
$a2 = (int)$arrN[0]%100;

 if($a1<=12 && $a2<=12 && $a1 >0 && $a2>0){
   echo "AMBIGUOUS"."\n";
 }
 elseif( $a1<=12 && $a1 >0 && $a2>=0){
   echo "MMYY"."\n";
 }
 elseif($a2<=12 && $a1 >=0 && $a2>0){
   echo "YYMM"."\n";
 }
 else{
   echo"NA"."\n";
}
?>