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)
	k := nextInt()
	dp := make([]float64, k+6)
	for i := k - 1; i >= 0; i-- {
		for j := i + 1; j < i+7; j++ {
			dp[i] += dp[j] / 6
		}
		dp[i]++
	}
	fmt.Println(dp[0])
}

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

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