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)
    {
        var nk = Console.ReadLine().Split();
        var n = int.Parse(nk[0]);
        var k = int.Parse(nk[1]);
        var s = Console.ReadLine();

        var a = s.Substring(0, k - 1);
        var b = s.Substring(k - 1, 1).ToLower();
        var c = s.Substring(k);
        Console.WriteLine(a + b + c);
    }
}