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.Scanner;

public class Main {

	public static void main(String[] args) {
		System.out.println(new Main().doWork(args));
	}

	public String doWork(String[] args) {
		Scanner reader = new Scanner(System.in);

		int n = reader.nextInt();
		int k = reader.nextInt();
		String ch = reader.next();

		reader.close();

		return ch.substring(0, k-1) + ch.substring(k-1, k+1-1).toLowerCase() + ch.substring(k+1-1);
	}
}