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: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

class Program
{

    static void Main()
    {
        var sc = new Scanner();
        int n = sc.Int();
        Console.WriteLine(800 * n - 200 * (n / 15));

    }
}
static class Extentions
{
    public static IEnumerable<T> Outpuut<T>(this IEnumerable<T> source)
    {
        foreach (var item in source)
        {
            Console.WriteLine(item);
        }
        return source;
    }
    public static T Print<T>(this T obj)
    {
        Console.WriteLine(obj);
        return obj;
    }
}
public class Scanner
{
    public Scanner()
    {
        byte[] inputBuffer = new byte[1024];
        System.IO.Stream inputStream = Console.OpenStandardInput(inputBuffer.Length);
        Console.SetIn(new System.IO.StreamReader(inputStream, Console.InputEncoding, false, inputBuffer.Length));
    }
    string[] buffer = new string[0];
    int index = 0;
    public char[] SplitChars { get; set; }
    public string String()
    {
        if (index < buffer.Length) return buffer[index++];
        string line = "";
        while (line == "") line = Console.ReadLine();
        if (line == null) return null;
        buffer = line.Split(SplitChars, StringSplitOptions.RemoveEmptyEntries);
        index = 0;
        return buffer[index++];
    }
    public string[] StringArray(int count) { return NextArray(count, x => x); }
    public void Skip(int count) { for (int i = 0; i < count; i++) String(); }
    public T Next<T>(Func<string, T> parser) { return parser(String()); }
    public T[] NextArray<T>(int count, Func<string, T> parser)
    {
        var arr = new T[count];
        for (int i = 0; i < count; i++) arr[i] = Next(parser);
        return arr;
    }
    public int Int() { return Next(int.Parse); }
    public int[] IntArray(int count) { return NextArray(count, int.Parse); }
    public double Double() { return Next(double.Parse); }
    public double[] DoubleArray(int count) { return NextArray(count, double.Parse); }
}