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;

namespace AtCoder
{
	public class Program
	{
		static void Main(string[] args)
		{
			int[] vs = Console.ReadLine().Split().Select(p => int.Parse(p)).ToArray();
			int N = vs[0];
			int K = vs[1];
			for (int i = 0; i < N; i++) {
				char c = (char)Console.Read();
				Console.Write(i + 1 == K ? char.ToLower(c) : c);
			}
			Console.WriteLine();
		}
	}
}