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 sc = new Scanner(System.in);
        int N = sc.nextInt();
        int K = sc.nextInt();
        String S = sc.next();
        sc.close();

        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < N; i++) {
            char s = S.charAt(i);
            if (i == K - 1) {
                switch (String.valueOf(s)) {
                    case "A":
                        sb.append("a");
                        break;
                    case "B":
                        sb.append("b");
                        break;
                    case "C":
                        sb.append("c");
                        break;
                    default:
                        continue;
                }
            } else {
                sb.append(String.valueOf(s));
            }
        }

        System.out.println(sb.toString());

    }
}