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 app1
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] NK = Console.ReadLine().Split(' ');
            int N = int.Parse(NK[0]);
            int K = int.Parse(NK[1]);
            char[] S = new char[N];

            S = Console.ReadLine().ToCharArray();

            K -= 1;

            if(K >= 0)
            {
                switch (S[K])
                {
                    case 'A':
                        S[K] = 'a';
                        break;
                    case 'B':
                        S[K] = 'b';
                        break;
                    case 'C':
                        S[K] = 'C';
                        break;
                    default:
                        break;
                }
            }
            string str = new string(S);

            Console.WriteLine($"{str}");
        }
    }
}