package main

import (
	"bufio"
	"fmt"
	"math/rand"
	"os"
	"strconv"
	"time"
)

var sc = bufio.NewScanner(os.Stdin)

func main() {
	sc.Split(bufio.ScanWords)
	n, k := nextInt(), nextInt()
	r := rand.New(rand.NewSource(time.Now().UnixNano()))
	yW, tW := 0, 0
	for i := 0; i < 4000000; i++ {
		y, t := 0, 0
		for j := 0; j < n; j++ {
			y += r.Intn(6) + 1
		}

		for j := 0; j < n-k; j++ {
			t += r.Intn(6) + 1
		}
		for j := 0; j < k; j++ {
			t += r.Intn(3) + 4
		}
		if y > t {
			yW++
		} else if t > y {
			tW++
		}
	}
	fmt.Println(float64(tW) / 4000000)
}

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

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