package no058;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int k = sc.nextInt();
		double[][][] dp = new double[2][n+1][100];
		int[][] dice = {{4,5,6,4,5,6},{1,2,3,4,5,6}};
		for(int i=0;i<2;i++) {
			dp[i][0][0] = 1;
			for(int j=0;j<n;j++) {
				int d = 1;
				if (i == 0 && j < k) {
					d = 0;
				}
				for(int l=0;l<70;l++) {
					for(int m=0;m<6;m++) {
						dp[i][j+1][l+dice[d][m]] += dp[i][j][l] / 6;
					}
				}
			}
		}
		//System.out.println(Arrays.deepToString(dp));
		double ans = 0;
		for(int i=0;i<100;i++) {
			for(int j=0;j<i;j++) {
				ans += dp[0][n][i] * dp[1][n][j];
			}
		}
		System.out.println(ans);
	}

}