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"
    "io"
    "os"
)

type BufferedWriter interface {
    Printf(format string, a ...interface{})
    Flush()
}

type writerImpl struct {
    *bufio.Writer
}

func NewBufferedWriter(writer io.Writer) BufferedWriter {
    return &writerImpl{Writer: bufio.NewWriter(writer)}
}

func (impl *writerImpl) Printf(f string, a ...interface{}) {
    fmt.Fprintf(impl.Writer, f, a...)
}

func (impl *writerImpl) Flush() {
    impl.Writer.Flush()
}

type WordScanner interface {
    NextInt() int
    NextInt64() int64
    NextString() string
}

type wordScannerImpl struct {
    *bufio.Scanner
}

func NewWordScanner(reader io.Reader) WordScanner {
    s := bufio.NewScanner(reader)
    s.Split(bufio.ScanWords)
    return &wordScannerImpl{Scanner: s}
}

func (impl *wordScannerImpl) NextInt() int {
    impl.Scan()
    bb := impl.Bytes()
    i := 0
    for _, b := range bb {
        i *= 10
        i += int(b - '0')
    }
    return i
}

func (impl *wordScannerImpl) NextInt64() int64 {
    impl.Scan()
    bb := impl.Bytes()
    i := int64(0)
    for _, b := range bb {
        i *= 10
        i += int64(b - '0')
    }
    return i
}

func (impl *wordScannerImpl) NextString() string {
    impl.Scan()
    return impl.Text()
}

var reader = NewWordScanner(os.Stdin)
var writer = NewBufferedWriter(os.Stdout)

func main() {
    defer writer.Flush()
    x := reader.NextInt64()
    writer.Printf("%d\n", sol(x))
}

func sol(x int64) int64 {
    h500 := x / 500
    x = x % 500
    h5 := x / 5
    return (h500 * 1000) + (h5 * 5)
}