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;

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

        char[] c = s.ToCharArray();
        c[k - 1] = (char)((int)c[k - 1] + 32);
      
        s = new String(c);
        Console.WriteLine(s);
    }
}