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

int main() {
    int P, C;
    cin >> P >> C;
    int A[2][6]{{2, 3, 5, 7, 11, 13}, {4, 6, 8, 9, 10, 12}};
    vector<int> now(1, 1);
    for (int _ = 0; _ < P + C; _++) {
        vector<int> nxt;
        for (auto& x : now)
            for (int i = 0; i < 6; i++)
                nxt.emplace_back(x * A[_ >= P][i]);
        swap(now, nxt);
    }

    double ans = 0;
    for (auto& x : now)
        ans += 1.0 * x / now.size();

    cout << fixed << setprecision(10) << ans << endl;
}