package main

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

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
	return scanner
}
func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextUint64(scanner *bufio.Scanner) uint64 {
	i, _ := strconv.ParseUint(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	cnt := 0
	if os.Getenv("MASPY") == "ますピ" {
		fp, _ = os.Open(os.Getenv("BEET_THE_HARMONY_OF_PERFECT"))
		cnt = 1
	}
	if os.Getenv("MASPYPY") == "ますピッピ" {
		wfp, _ = os.Create(os.Getenv("NGTKANA_IS_GENIUS10"))
	}
	scanner := getScanner(fp)
	writer := bufio.NewWriter(wfp)
	solve(scanner, writer)
	for i := 0; i < cnt; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
	writer.Flush()
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	n := getNextInt(scanner)
	k := getNextInt(scanner)
	taro := make([]float64, n*6+1)
	taro[0] = 1
	jiro := make([]float64, n*6+1)
	jiro[0] = 1
	for t := 0; t < n; t++ {
		for i := n * 6; i > t; i-- {
			taro[i] = 0
			jiro[i] = 0
			for j := 1; j <= 6; j++ {
				if i-j >= 0 {
					jiro[i] += jiro[i-j] / 6
				}
			}
			if t < k {
				for j := 4; j <= 6; j++ {
					if i-j >= 0 {
						taro[i] += taro[i-j] / 3
					}
				}
				continue
			}
			for j := 1; j <= 6; j++ {
				if i-j >= 0 {
					taro[i] += taro[i-j] / 6
				}
			}
		}
		for i := t; i >= 0; i-- {
			taro[i] = 0
			jiro[i] = 0
		}
	}
	var ans float64
	for i := 1; i < n*6+1; i++ {
		s := 0.0
		for j := 1; j < i; j++ {
			s += jiro[j]
		}
		ans += s * taro[i]
	}
	fmt.Fprintln(writer, ans)
}