#include "bits/stdc++.h"
using namespace std;

typedef long long Int;
#define REP(i,n) for(int (i)=0;(i)<(int)(n);++(i))

int main() {
	int N;
	int K;
	cin >> N >> K;

	const int MAX = 6 * N;
	int val_a[6] = { 1, 2, 3, 4, 5, 6 };
	int val_b[6] = { 4, 5, 6, 4, 5, 6 };

	vector<double> p1(MAX + 1);
	vector<double> p2(MAX + 1);
	
	p1[0] = 1.0;
	p2[0] = 1.0;

	REP(n, N) {
		vector<double> next(MAX + 1);
		int *val = n < K ? val_b : val_a;
		REP(m, MAX + 1) {
			REP(ii, 6) {
				int i = val[ii];
				if (p1[m] > 0) {
					next[m + i] += p1[m] / 6;
				}
			}
		}
		p1 = next;
	}
	REP(n, N) {
		vector<double> next(MAX + 1);
		REP(m, MAX + 1) {
			REP(ii, 6) {
				int i = val_a[ii];
				if (p2[m] > 0) {
					next[m + i] += p2[m] / 6;
				}
			}
		}
		p2 = next;
	}

	double win = 0;
	REP(m1, MAX + 1) REP(m2, MAX + 1) if (m1 > m2) win += p1[m1] * p2[m2];
	printf("%.6f\n", win);
}