#include <iostream>
#include <vector>
#include <map>
#include <algorithm>
#include <iomanip>
using namespace std;

typedef long long LL;

int main(){
    int v1[] = {2,3,5,7,11,13};
    int v2[] = {4,6,8,9,10,12};
    int P, C;
    cin >> P >> C;
    map<LL,LL> prev;
    map<LL,LL> next;
    prev[1] = 1;
    for(int i = 0; i < P; i++){
        for(int j = 0; j < 6; j++){
            for(auto& p : prev){
                next[p.first * v1[j]] += p.second;
            }
        }
        prev.swap(next);
        next.clear();
    }
    for(int i = 0; i < C; i++){
        for(int j = 0; j < 6; j++){
            for(auto& p : prev){
                next[p.first * v2[j]] += p.second;
            }
        }
        prev.swap(next);
        next.clear();
    }
    LL total = 0;
    for(auto& p : prev){
        total += p.second;
    }
    double exp = 0.0;
    for(auto& p : prev){
        exp += p.first * (double)(p.second) / total;
    }
    cout << setprecision(13) << exp << endl;
    return 0;
}