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;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            
            string inputbuf1 = Console.ReadLine();
            string inputbuf2 = Console.ReadLine();
            //string inputbuf1 = "5 3";
            //string inputbuf2 = "ABCAB";

            string[] inputdata = inputbuf1.Split(' ');
            int N = Convert.ToInt32(inputdata[0]);
            int K = Convert.ToInt32(inputdata[1]);
            string outstr = inputbuf2.Substring(0, K-1 ) + Char.ToLower(inputbuf2[K-1]);
            outstr = outstr + inputbuf2.Substring(K);


            Console.WriteLine(outstr);
            //Console.ReadKey();

        }
    }
}