#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <cstdio>
#include <cmath>
using namespace std;
typedef long long ll;
#define rep(i,n) for(int i=0;i<(n);i++)
const int INF = 1e9;

int P, C;
int p[6] = {2, 3, 5, 7, 11, 13};
int c[6] = {4, 6, 8, 9, 10, 12};
ll ans = 0;

void dfs(ll sum, int dep){
	if(dep == P + C){
		ans += sum;
		return;
	}

	if(dep < P){
		rep(i, 6) dfs(sum * p[i], dep + 1);
	}else{
		rep(i, 6) dfs(sum * c[i], dep + 1);
	}
	return;
}

int main(void){
	cin >> P >> C;
	dfs(1, 0);
	double E = (double)ans / pow(6.0, P + C);
	printf("%.10f\n", E);
	return 0;
}