#include<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#include<map>
#include<string>
#include<algorithm>
#include<functional>
using namespace std;
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define INF 1<<30
#define MP make_pair
#define mp make_pair
#define pb push_back
#define PB push_back
#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define ll long long
#define ull unsigned long long
	int pri_d[6] = {2,3,5,7,11,13};
	int fuc_d[6] = {4,6,8,9,10,12};

double dfs(int p,int c){
	double sum=0;
	if (p==0 && c==0) return 1;
	else if (p!=0) REP(i,6) sum+=(double)pri_d[i]/6*dfs(p-1,c);
	else if (c!=0) REP(i,6) sum+=(double)fuc_d[i]/6*dfs(p,c-1);
	return sum;
}
int main(){
	int P,C;
	cin >> P >> C;
	printf("%.15f\n",dfs(P,C));
	return 0;
}