package main

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

var sc = bufio.NewScanner(os.Stdin)

func main() {
	sc.Split(bufio.ScanWords)
	n, cheat := nextInt(), nextInt()
	zdp, tdp := make([]float64, 61), make([]float64, 61)
	zdp[0], tdp[0] = 1, 1

	for i := 0; i < n; i++ {
		for j := 54; j >= 0; j-- {
			for k := 1; k < 7; k++ {
				zdp[j+k] += zdp[j] / 6
			}
			zdp[j] = 0
		}
	}

	for i := 0; i < n-cheat; i++ {
		for j := 54; j >= 0; j-- {
			for k := 1; k < 7; k++ {
				tdp[j+k] += tdp[j] / 6
			}
			tdp[j] = 0
		}
	}

	for i := 0; i < cheat; i++ {
		for j := 54; j >= 0; j-- {
			for k := 4; k < 7; k++ {
				tdp[j+k] += tdp[j] / 3
			}
			tdp[j] = 0
		}
	}

	ans := float64(0)
	for i := n - cheat + (cheat * 4); i < 61; i++ {
		for j := i - 1; j >= n; j-- {
			ans += tdp[i] * zdp[j]
		}
	}
	fmt.Println(ans)
}

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

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