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.*;

class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    
    int n = sc.nextInt();
    int k = sc.nextInt();
    String s = sc.next();
    if (s.charAt(k-1) == 'A'){
      System.out.println(s.substring(0,k-1)+"a"+s.substring(k));
    }
    if (s.charAt(k-1) == 'B'){
      System.out.println(s.substring(0,k-1)+"b"+s.substring(k));
    }
    if (s.charAt(k-1) == 'C'){
      System.out.println(s.substring(0,k-1)+"c"+s.substring(k));
    }
  }
}