#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	double dp1[100] = {}, dp2[100] = {};
	dp1[0] = 1; dp2[0] = 1;
	int n, k;
	cin >> n >> k;
	for (int i = 0; i < n; i++) {
		for (int j = 90; j >= 0; j--) {
			for (int l = 1; l <= 6; l++) {
				dp1[j + l] += dp1[j] / 6.0;
			}
			dp1[j] = 0;
		}
	}
	for (int i = 0; i < n; i++) {
		for (int j = 90; j >= 0; j--) {
			if (i < k) {
				for (int l = 4; l <= 6; l++) {
					dp2[j + l] += dp2[j] / 3.0;
				}
				dp2[j] = 0;
			} else {
				for (int l = 1; l <= 6; l++) {
					dp2[j + l] += dp2[j] / 6.0;
				}
				dp2[j] = 0;
			}
		}
	}
	double ans = 0;
	for (int i = 0; i < 100; i++) {
		for (int j = i + 1; j < 100; j++) {
			ans += dp1[i] * dp2[j];
		}
	}
	cout << setprecision(20) << fixed << ans << endl;
	return 0;
}