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

int64_t p[] = {2, 3, 5, 7, 11, 13};
int64_t c[] = {4, 6, 8, 9, 10, 12};

int P, C;

double recursive(int pos, double val) {
	if(pos >= P + C) {
		return val;
	}
	double a = 0;
	for(int i = 0; i < 6; i++) {
		a += recursive(pos + 1, val * (pos < P ? p[i] : c[i]) );
	}
	return a / 6;
}

int main() {
	cin >> P >> C;
	cout << fixed << setprecision(15) << recursive(0, 1) << endl;
	return 0;
}