Problem:
Score : 200 points

Problem Statement

Takahashi loves gold coins. He gains 1000 happiness points for each 500-yen coin he has and gains 5 happiness points for each 5-yen coin he has. (Yen is the currency of Japan.)

Takahashi has X yen. If he exchanges his money so that he will gain the most happiness points, how many happiness points will he earn?

(We assume that there are six kinds of coins available: 500-yen, 100-yen, 50-yen, 10-yen, 5-yen, and 1-yen coins.)

Constraints

0 \leq X \leq 10^9

X is an integer.

Input

Input is given from Standard Input in the following format:

X

Output

Print the maximum number of happiness points that can be earned.

Sample Input 1

1024

Sample Output 1

2020

By exchanging his money so that he gets two 500-yen coins and four 5-yen coins, he gains 2020 happiness points, which is the maximum number of happiness points that can be earned.

Sample Input 2

0

Sample Output 2

0

He is penniless - or yenless.

Sample Input 3

1000000000

Sample Output 3

2000000000

He is a billionaire - in 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 static System.Console;
using static System.Math;

namespace Atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                Solve.Answer();
            }
            catch (Exception ex)
            {
                WriteLine(ex.ToString());
            }
        }
    }

    public class Solve
    {
        public static void Answer()
        {
            var X = IO_ShortCut.ReadInt;

            var a = X / 500;
            var b = (X - a * 500) / 5;
            WriteLine(1000 * a + 5 * b);
        }
    }

    public class IO_ShortCut
    {
        #region Input
        public static string ReadString => ReadLine();
        public static int ReadInt => int.Parse(ReadLine());
        public static long ReadLong => long.Parse(ReadLine());
        public static double ReadDouble => double.Parse(ReadLine());

        public static List<string> ReadSplitString => ReadLine().Split().ToList();
        public static List<int> ReadSplitInt => ReadLine().Split().Select(s => int.Parse(s)).ToList();
        public static List<long> ReadSplitLong => ReadLine().Split().Select(s => long.Parse(s)).ToList();
        public static List<double> ReadSplitdouble => ReadLine().Split().Select(s => double.Parse(s)).ToList();
        #endregion

        #region Output
        public static void OutJoinSpace<T>(IEnumerable<T> list) => WriteLine(string.Join(" ", list));
        #endregion
    }

    public class Mod
    {
        // 割る数の定義
        private readonly static long M = 1000000007;

        // 足し算?
        public static long Add(long a, long b)
        {
            var result = a + b;
            if (a + b < 0)
                return result % M == 0 ? result % M : result % M + M;
            else if (a + b >= M)
                return result % M;
            else
                return result;
        }
        // 引き算
        // 割られる数が負になると余りの定義的にダメなので実装
        public static long Sub(long a, long b) => (a - b) % M >= 0 ? (a - b) % M : (a - b) % M + M;
        // 掛け算
        //    public static long Multi(long a, long b)
        //    {

        //    }
    }

}