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[]) {
    int rep = 1;
    if( args.length > 0 ) { rep = Integer.parseInt(args[0]); }
    (new Main()).__solve(rep);
  }

  void __solve(int rep) {

    try (
      Scanner cin = new Scanner(System.in);
    ) {

      for( int i = 0; i < rep; ++i ) {
        __solve(cin);
      }

    }

  }

  void __solve(Scanner cin) {
	  int N = cin.nextInt();
	  int K = cin.nextInt();
	  String s = cin.next();
	  String ans = "";
	  for( int i = 0; i < N; ++i ) {
		  if( i + 1 == K ) {
			  ans += (char)(s.charAt(i) - 'A' + 'a');
		  }
		  else {
			  ans += s.charAt(i);
		  }
	  }
	  System.out.println(ans);
  }

}