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.Globalization;
using System.IO;
using System.Linq;

namespace CF317
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            var sr = new InputReader(Console.In);
            //var sr = new InputReader(new StreamReader("input.txt"));
            var task = new Task();
            using (var sw = Console.Out)
            //using (var sw = new StreamWriter("output.txt"))
            {
                task.Solve(sr, sw);
                //Console.ReadKey();
            }
        }
    }

    internal class Task
    {
        public void Solve(InputReader sr, TextWriter sw)
        {
            var n = sr.NextInt32();
            var x = 0L;
            var y = 0L;
            for (var i = 1; i <= n; i++) {
                if (i % 15 == 0) {
                    y += 200;
                }
                x += 800;
            }

            sw.WriteLine(x - y);
        }
    }
}

internal class InputReader : IDisposable
{
    private bool isDispose;
    private readonly TextReader sr;

    public InputReader(TextReader stream)
    {
        sr = stream;
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    public string NextString()
    {
        var result = sr.ReadLine();
        return result;
    }

    public int NextInt32()
    {
        return Int32.Parse(NextString());
    }

    public long NextInt64()
    {
        return Int64.Parse(NextString());
    }

    public string[] NextSplitStrings()
    {
        return NextString()
            .Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
    }

    public T[] ReadArray<T>(Func<string, CultureInfo, T> func)
    {
        return NextSplitStrings()
            .Select(s => func(s, CultureInfo.InvariantCulture))
            .ToArray();
    }

    public T[] ReadArrayFromString<T>(Func<string, CultureInfo, T> func, string str)
    {
        return
            str.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries)
                .Select(s => func(s, CultureInfo.InvariantCulture))
                .ToArray();
    }

    protected void Dispose(bool dispose)
    {
        if (!isDispose)
        {
            if (dispose)
                sr.Close();
            isDispose = true;
        }
    }

    ~InputReader()
    {
        Dispose(false);
    }
}