#include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;

static const int primes[] = { 2, 3, 5, 7, 11, 13 };
static const int composites[] = { 4, 6, 8, 9, 10, 12 };

long long sum(long long product, int p, int c) {
	if (p > 0) {
		long long result = 0;
		for (int i = 0; i < 6; ++i) {
			result += product * primes[i];
		}
		return sum(result, p - 1, c);
	} else if (c > 0) {
		long long result = 0;
		for (int i = 0; i < 6; ++i) {
			result += product * composites[i];
		}
		return sum(result, p, c - 1);
	}
	return product;
}

int main() {
	int p, c;
	cin >> p >> c;
	double result = (double)sum(1, p, c) / pow(6, p + c);
	cout << setprecision(10) << result << endl;
	return 0;
}