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 test
{
  class Program
  {
   	static void Main(string[] args)
   	{
            string[] a = Console.ReadLine().Split(' ');
            string s = Console.ReadLine();
            char[] str = s.ToCharArray();
            int n = int.Parse(a[0]);
            int k = int.Parse(a[1]);

            if (str[k - 1] == 'A')
            {
                str[k - 1] = 'a';
            }
            else if (str[k - 1] == 'B')
            {
                str[k - 1] = 'b';
            }
            else
            {
                str[k - 1] = 'c';
            }

           Console.WriteLine(new String(str));
   	}
  }
}