Problem:
Score : 100 points

Problem Statement

Snuke has a favorite restaurant.

The price of any meal served at the restaurant is 800 yen (the currency of Japan), and each time a customer orders 15 meals, the restaurant pays 200 yen back to the customer.

So far, Snuke has ordered N meals at the restaurant.
Let the amount of money Snuke has paid to the restaurant be x yen, and let the amount of money the restaurant has paid back to Snuke be y yen.
Find x-y.

Constraints

1 ≤ N ≤ 100

Input

The input is given from Standard Input in the following format:

N

Output

Print the answer.

Sample Input 1

20

Sample Output 1

15800

So far, Snuke has paid 16000 yen, and the restaurant has paid back 200 yen. Thus, the answer is 15800.

Sample Input 2

60

Sample Output 2

47200

Snuke has paid 48000 yen for 60 meals, and the restaurant has paid back 800 yen.

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;

namespace abc055
{
    public class Program
    {
        public static void Main(string[] args)
        {
            int n = Convert.ToInt32(Console.ReadLine());
            long p = 1;

            long mod= Convert.ToInt64(Math.Pow(Convert.ToDouble(10), Convert.ToDouble(9)) + Convert.ToDouble(7));
            
            for (int i = 1; i <= n; i++)
            {
                p = p * Convert.ToInt64(i);
                p = p % mod;               
            }

            Console.WriteLine(p.ToString());
        }
    }
}