Problem:
Score : 100 points

Problem Statement

It is known that the area of a regular dodecagon inscribed in a circle of radius a is 3a^2.

Given an integer r, find the area of a regular dodecagon inscribed in a circle of radius r.

Constraints

1 \leq r \leq 100

r is an integer.

Input

Input is given from Standard Input in the following format:

r

Output

Print an integer representing the area of the regular dodecagon.

Sample Input 1

4

Sample Output 1

48

The area of the regular dodecagon is 3 \times 4^2 = 48.

Sample Input 2

15

Sample Output 2

675

Sample Input 3

80

Sample Output 3

19200

Solution in C# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;

namespace question4
{
    class Program
    {
        static void Main(string[] args)
        {

            int flag = 1;

            int n = int.Parse(Console.ReadLine());
            string[] str = Console.ReadLine().Split(' ');
            string[] ans = str;
            int half = (n / 2) + 1;

            /*
            for (int i = (n-1); i >=half; i--)
            {
                ans[i] = str[i];
            }
            */
            for (int i = n - 1; i >= 0; i--)
            {
                if (i > (n / 2 - 1))
                {
                    ans[i] = str[i];
                }
                else
                {
                    ans[i] = (int.Parse(str[i]) ^ int.Parse(str[(i + 1) * 2 - 1])).ToString();

                }

            }

            int m = 0;

            string b = "";
            for (int i = 0; i < n; i++)
            {
                if (ans[i] == "1")
                {
                    m += 1;
                    b = b + (i + 1).ToString() + " ";
                }
            }
            /*
            for (int i = 1; i < (n/2+1); i++)
            {
                int delta = (n / i);
                int count = 0;
                for (int j=1;j< (delta+1); j++)
                {
                    count += int.Parse(ans[i * j-1]);

                }
                if (count%2 != int.Parse(str[i-1])) flag = 0;                
            }
            */
            if (flag == 1)
            {
                Console.WriteLine(m);
                Console.WriteLine(b);

            }
            else Console.WriteLine("-1");
           // Console.ReadLine();
        }
    }
}