#include <cstdio>
#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <string>
#include <cstring>
#include <sstream>
#include <algorithm>
#include <functional>
#include <queue>
#include <stack>
#include <cmath>
#include <iomanip>
#include <list>
#include <tuple>
#include <bitset>

using namespace std;

inline bool cheak(int x, int y, int xMax, int yMax){ return x >= 0 && y >= 0 && xMax > x && yMax > y; }
template<class T> inline string toString(T x) { ostringstream sout; sout << x; return sout.str(); }
template<class T> inline T sqr(T x) { return x*x; }

typedef pair<int, int> P;
typedef tuple<int, int, int> T;
typedef long long ll;
typedef unsigned long long ull;
inline ll toInt(string s) { ll v; istringstream sin(s); sin >> v; return v; }

#define For(i,a,b)	for(int (i) = (a);i < (b);(i)++)
#define rep(i,n)	For(i,0,n)
#define clr(a)		memset((a), 0 ,sizeof(a))
#define mclr(a)		memset((a), -1 ,sizeof(a))
#define all(a)		(a).begin(),(a).end()
#define sz(a)		(sizeof(a))
#define Fill(a,v)	fill((int*)a,(int*)(a+(sz(a)/sz(*(a)))),v)

const int dx[8] = { 1, 0, -1, 0, 1, 1, -1, -1 }, dy[8] = { 0, -1, 0, 1, -1, 1, -1, 1 };
const int mod = 1000000007;
const int INF = 1e9;


int a[] = { 2, 3, 5, 7, 11, 13 };
int b[] = { 4, 6, 8, 9, 10, 12 };
int p,c;
int d[20];
double sum = 0;
double counter = 0;

void dfs(int t){

	if (t == p + c){
		double tmp = 1;
		rep(i, p + c)tmp *= d[i];
		sum += tmp;
		counter++;
		return;
	}


	rep(i, 6){
		if (t < p)
			d[t] = a[i];
		else
			d[t] = b[i - p];

		dfs(t + 1);
	}
}

int main()
{  
	cin >> p >> c;
	
	dfs(0);
	cout << setprecision(40) << double(sum) /  double(counter) << endl;

	return 0;
}