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.Linq;

namespace agc030_a
{
    class Program
    {
        static void Main(string[] args)
        {
            var text = Console.ReadLine();
            var list = text.Split(' ').ToList();

            var r = int.Parse(list[0]);
            var n = int.Parse(list[1]);

            text = Console.ReadLine();

            var line = text.Substring(0, n - 1) + text.Substring(n - 1, 1).ToLower();
            if (r != n){
                line = line + text.Substring(n, r - n);
            }
            
            Console.WriteLine(line);
        }
    }
}