package main

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

var sc = bufio.NewScanner(os.Stdin)
var rdr = bufio.NewReaderSize(os.Stdin, 1000000)

func main() {
	sc.Split(bufio.ScanWords)
	n := nextUint64()
	tax := n * 8
	s1 := fmt.Sprint(n)
	s2 := fmt.Sprint(tax)
	var b []byte
	up := 0
	for i := len(s1) - 1; i >= 0 || up == 1; i-- {
		v1, _ := strconv.Atoi(string(s1[i]))
		v2 := 0
		if i-2 >= 0 {
			v2, _ = strconv.Atoi(string(s2[i-2]))
		}
		c := fmt.Sprint((v1 + v2 + up) % 10)
		b = append([]byte{c[0]}, b...)
		if v1+v2 >= 10 {
			up = 1
		} else {
			up = 0
		}
	}

	fmt.Printf("%s.%s", string(b), s2[len(s2)-2:len(s2)])

}

func nextLine() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	i, _ := strconv.Atoi(nextLine())
	return i
}

func nextInt64() int64 {
	i, _ := strconv.ParseInt(nextLine(), 10, 64)
	return i
}

func nextUint64() uint64 {
	i, _ := strconv.ParseUint(nextLine(), 10, 64)
	return i
}

func nextFloat() float64 {
	f, _ := strconv.ParseFloat(nextLine(), 64)
	return f
}

func readLine() string {
	buf := make([]byte, 0, 1000000)
	for {
		l, p, e := rdr.ReadLine()
		if e != nil {
			panic(e)
		}
		buf = append(buf, l...)
		if !p {
			break
		}
	}
	return string(buf)
}