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-mcs 6.8.0.105) (judge verdict: Accepted)

public class Hello{
    public static void Main(){
        string str = System.Console.ReadLine();
        int X = int.Parse(str);
        //var N = int.Parse(System.Console.ReadLine());
        int ans = 0;
        
        while(X > 0){
            if(X>=500){
                X -= 500;
                ans += 1000;
            }else if(X>=5){
                X -= 5;
                ans += 5;
            }else{
                break;
            }
        }
        
        System.Console.WriteLine(ans);
    }
}