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 ABC126A
{
    class Program
    {
        static void Main(string[] args)
        {

            int[] input = Console.ReadLine().Split().Select(int.Parse).ToArray();

            int N = input[0];
            int K = input[1];

            string S = Console.ReadLine();

            string ans = "";
            for(int i = 1; i <= N; i++)
            {
                if (i == K) ans += S.ToLowerInvariant()[i - 1];
                else ans += S[i - 1];
            }

            Console.WriteLine(ans);
            Console.ReadKey();
        }
    }
}