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 Rust (1.15.1) (judge verdict: Accepted)

//! Generic utility for reading data from standard input, based on [voxl's
//! stdin wrapper](http://codeforces.com/contest/702/submission/19589375).
#![allow(unused_imports)]
use std::cmp::{max, min};
use std::collections::{HashMap, HashSet, VecDeque};
use std::io::{self, BufWriter, Write};

#[derive(Default)]
struct Scanner {
    #[allow(dead_code)]
    buffer: Vec<String>,
}

impl Scanner {
    #[allow(dead_code)]
    fn next<T: std::str::FromStr>(&mut self) -> T {
        loop {
            if let Some(token) = self.buffer.pop() {
                return token.parse().ok().expect("Failed parse");
            }
            let mut input = String::new();
            io::stdin().read_line(&mut input).expect("Failed read");
            self.buffer = input.split_whitespace().rev().map(String::from).collect();
        }
    }
}

fn solve<T: Write>(scan: &mut Scanner, out: &mut BufWriter<T>) {
    // CODE HERE
    let x: u64 = scan.next();
    let five_hundreds = x / 500;
    let balance = x % 500;
    let fives = balance / 5;

    let happiness = five_hundreds * 1000 + fives * 5;
    writeln!(out, "{}", happiness);
}

fn main() {
    let mut scan = Scanner::default();
    let mut out = BufWriter::new(io::stdout());
    solve(&mut scan, &mut out);
}