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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC_126_A___Changing_a_Character
{
    class Program
    {
        static void Main(string[] args)
        {
            int N, K;
            string S;
            var M = Console.ReadLine().Split(' ');
            N = int.Parse(M[0]);
            K = int.Parse(M[1]);
            Console.WriteLine();
            S = Console.ReadLine();
           

            char[] cs = S.ToCharArray();
            if (cs[K - 1] == 'A')   cs[K-1] = 'a';
            else if (cs[K - 1] == 'B') cs[K - 1] = 'b';
            else cs[K - 1] = 'b';
            Console.WriteLine(cs);
            Console.ReadLine();

        }
    }
}