package main

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

var sc = bufio.NewScanner(os.Stdin)
var out = bufio.NewWriter(os.Stdout)

func F(x int) int {
	if x == 1 {
		return 0
	}
	// x >= 2
	if x%2 == 0 {
		d := Max(Ceil(x, 2)-2, 0)
		return x + 8*d
	} else {
		return F(x+1) + 1
	}
}

func main() {
	buf := make([]byte, 1024*1024)
	sc.Buffer(buf, bufio.MaxScanTokenSize)
	sc.Split(bufio.ScanWords)

	x := nextInt()

	ans := F(x)
	PrintInt(ans)
}

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

func PrintInt(x int) {
	defer out.Flush()
	fmt.Fprintln(out, x)
}

func Max(x, y int) int {
	if x < y {
		return y
	}
	return x
}

func Ceil(x, y int) int {
	return (x + y - 1) / y
}