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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

function Main(input) {
  input = input.split("\n");
  var tmp = input[0].split(" ");

  var K = parseInt(tmp[1]);
  var S = input[1];

  if(K>1) {
    var upperK = S.charAt(K-1);
    var lowerK = upperK.toLowerCase();
    var s = S.replace(upperK, lowerK);

    var result = s;
    console.log(result);    
  }
}

//*この行以降は編集しないでください（標準入出力から一度に読み込み、Mainを呼び出します）

Main(require("fs").readFileSync("/dev/stdin", "utf8"));