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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

//const (
//	MaxIntValue = int(^uint(0) >> 1)
//)

func main() {
	X := readLineInt()[0]
	Result := 0

	for {
		if X-500 >= 0 {
			Result += 1000
			X -= 500
		} else if X-5 >= 0 {
			Result += 5
			X -= 5
		} else {
			break
		}
	}

	fmt.Println(Result)
}

/////////////////////////////////////////
var scanner = bufio.NewScanner(os.Stdin)

func init() {
	//scanner.Split(bufio.ScanWords)
}
func readLine() string {
	scanner.Scan()
	return scanner.Text()
}

func loop(start, end int, f func(i int)) {
	for i := start; i < end; i++ {
		f(i)
	}
}

func readLineInt() []int {
	result := make([]int, 0)
	for _, v := range strings.Split(readLine(), " ") {
		r, _ := strconv.Atoi(v)
		result = append(result, r)
	}
	return result
}