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.Linq;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args)
    {
        var inputs = Console.ReadLine().Split(' ');
        var N = int.Parse(inputs[0]);
        var K = int.Parse(inputs[1]);
        var S = Console.ReadLine();

        var ans = new System.Text.StringBuilder();
        for (int i = 0; i < S.Length; i++)
        {
            if (i == K - 1)
            {
                ans.Append(S[i].ToString().ToLower());
            }
            else
            {
                ans.Append(S[i]);
            }
        }

        Console.WriteLine(ans);
    }

}