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;

public class ChangingaCharacter
    {
        static void Main(string[] args)
        {
            string[] line1 = Console.ReadLine().Trim().Split(' ');
            var lengs = int.Parse(line1[0]);
            var target = int.Parse(line1[1]);
            string str = Console.ReadLine().Trim();
            string ans = null;

            for (int i = 0; i < lengs; i++)
            {
                if (i == target - 1)
                {
                    ans = ans + str[i].ToString().ToLower();
                }
                else
                {
                    ans = ans + str[i];
                }
            }
            Console.WriteLine(ans);
        }
    }