#include <iostream>
#include <cstdio>
typedef long long ll;
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)

int main() {
	int n, y;
	cin >> n >> y;
	double dp1[100][n * 6];
	double dp2[100][n * 6];
	dp1[0][0] = 1;
	dp2[0][0] = 1;
	int sumt = 0;
	int sumj = 0;
	double ans = 0;
	for (int i = 1; i <= n; ++i) {
		for (int j = 1; j <= 6*i; ++j) {
			if (i <= y) {
				for (int k = 4; k <= 6; k++) {
					if (j - k >= 0) {
						dp1[i][j] += dp1[i - 1][j - k] / 3.0;
					}
				}
			} else {
				for (int k = 1; k <= 6; k++) {
					if (j - k >= 0) {
						dp1[i][j] += dp1[i - 1][j - k] / 6.0;
					}
				}
			}
		}
	}
	for (int i = 1; i <= n; ++i) {
		for (int j = 1; j <= 6*i; ++j) {
			for (int k = 1; k <= 6; k++) {
				if (j - k >= 0) {
					dp2[i][j] += dp2[i - 1][j - k] / 6.0;
				}
			}
		}
	}

	for (sumt = 1; sumt <= 6 * n; ++sumt) {
		for (sumj=1; sumj < sumt; ++sumj) {
			ans += dp1[n][sumt] * dp2[n][sumj];
		}
}
cout << ans << endl;

}