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;

namespace ABC126A
{
    class Program
    {
        static void Main(string[] args)
        {
            int a, b;
            string[] ss = Console.ReadLine().Split(' ');
            a = int.Parse(ss[0]);
            b = int.Parse(ss[1]);
            
            string s = Console.ReadLine();
            if (s.Substring(b - 1, 1) == "A")
                Console.WriteLine(s.Substring(0, b - 1) + "a" + s.Substring(b, a - b));
            else if (s.Substring(b - 1, 1) == "B")
                Console.WriteLine(s.Substring(0, b - 1) + "b" + s.Substring(b, a - b));
            else
                Console.WriteLine(s.Substring(0, b - 1) + "c" + s.Substring(b, a - b));
            Console.ReadKey();
            
        }
    }
}