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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.*;
 
public class Main{
  public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    String nk = scanner.nextLine();
    String s = scanner.nextLine();
    int toLowerCaseIdx = Integer.parseInt(nk.split(" ")[1]);
    StringBuilder sb = new StringBuilder(s);
    sb.replace(toLowerCaseIdx-1,toLowerCaseIdx,s.substring(toLowerCaseIdx-1,toLowerCaseIdx).toLowerCase());
    System.out.println(sb);
  }
}