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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.*;


public class Main {
    public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);
      //文字列の長さ
      int n = sc.nextInt();
      //指定する文字の位置
      int k = sc.nextInt();
      sc.nextLine();
      
      //対象文字列
      String str = sc.nextLine();
      
      
      for(int i = 0;i < n;i++){
        if(i == k - 1){
          char c = str.charAt(i);
          String ans = String.valueOf(c);
          System.out.print(ans.toLowerCase());
        }else{
          System.out.print(str.charAt(i));
      }
      }
    }
}