import java.io.*;
import java.util.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int k = sc.nextInt();
        double[][] taro = new double[n + 1][n * 6 + 1];
        double[][] jiro = new double[n + 1][n * 6 + 1];
        taro[0][0] = 1;
        jiro[0][0] = 1;
        for (int i = 1; i <= n; i++) {
            for (int j = 0; j <= (i - 1) * 6; j++) {
                if (i <= k) {
                    for (int a = 4; a <= 6; a++) {
                        taro[i][j + a] += taro[i - 1][j] / 3;
                    }
                } else {
                    for (int a = 1; a <= 6; a++) {
                        taro[i][j + a] += taro[i - 1][j] / 6;
                    }
                }
                for (int a = 1; a <= 6; a++) {
                    jiro[i][j + a] += jiro[i - 1][j] / 6;
                }
            }
        }
        double[] sum = new double[n * 6 + 1];
        double ans = 0;
        for (int i = 1; i < sum.length - 1; i++) {
            sum[i] = sum[i - 1] + jiro[n][i];
            ans += sum[i] * taro[n][i + 1];
        }
        System.out.println(ans);
    }
}
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}