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

namespace Atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
           var firstLine = Console.ReadLine().Split(' ');
            var N = int.Parse(firstLine[0]);
            var K = int.Parse(firstLine[1]);
            var S = Console.ReadLine();
            for (int i = 0; i < S.Length; i++)
            {
                if (K-1 == i)
                {                    
                    Console.Write(char.ToLower(S[i]));
                    continue;
                }
                Console.Write(S[i]);
            }
        }

    }

    //var N = int.Parse(Console.ReadLine());
    //var S = Console.ReadLine();
    //var K = Console.ReadLine().Split(' ');
}