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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;

public class Hello
{
    private const int MOD_N = 1000000000 + 7;

    public static void Main()
    {
        var list = Console.ReadLine().Split(' ');
        var n = int.Parse(list[0]);
        var k = int.Parse(list[1]);
        var s = Console.ReadLine();

        var ans = new char[n];
        for (int i = 0; i < ans.Length; ++i)
        {
            var c = s[i];
            if (i == k - 1)
            {
                switch (c)
                {
                    case 'A':
                        c = 'a';
                        break;
                    case 'B':
                        c = 'b';
                        break;
                    case 'C':
                        c = 'c';
                        break;
                }
            }
            ans[i] = c;
        }

        Console.WriteLine(ans);
    }
}