#include <iostream>
#include <sstream>
#include <iomanip>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>
#include <numeric>
#include <iterator>
#include <functional>
#include <complex>
#include <queue>
#include <stack>
#include <cmath>
#include <cassert>
#include <cstring>
using namespace std;
typedef long long LL;
typedef complex<double> CMP;

class LastMarble { public:
	typedef pair<int,int>  rb;
	typedef map<rb,double> state;

	double winningChance(int red, int blue, int removed) 
	{
		state s;
		addNextStates( red, blue, 1.0, removed, s );
		return winChance(s);
	}

	double winChance( state& s )
	{
		if( s.empty() )
			return 1.0; // any value is ok because it will be multiplied by 0.0

		int r_plus_b = s.begin()->first.first + s.begin()->first.second;

		double lc = 1.0;
		for(int take=1; take<=min(3,r_plus_b); ++take)
		{
			state ns;
			for(state::iterator it=s.begin(); it!=s.end(); ++it)
				addNextStates(it->first.first, it->first.second, it->second, take, ns);

			double nowLoseChance = 0.0;
			for(state::iterator it=ns.begin(); it!=ns.end(); )
				if( it->first.first == 0 ) {
					nowLoseChance += it->second;
					ns.erase( it++ );
				} else {
					++it;
				}
	
			double continueChance = 1.0 - nowLoseChance;
			for(state::iterator it=ns.begin(); it!=ns.end(); ++it)
				it->second /= continueChance;
			double loseChance = nowLoseChance + winChance(ns)*continueChance;
			lc = min(lc, loseChance);
		}
		return 1.0 - lc;
	}

	void addNextStates(int r, int b, double p, int take, state& m)
	{
		if( take == 0 ) {
			m[rb(r,b)] += p;
			return;
		}

		state tmp;
		tmp[rb(r,b)] = p;

		while( take --> 0 )
		{
			state tmp2;
			state& tgt = (take ? tmp2 : m);
			for(state::iterator it=tmp.begin(); it!=tmp.end(); ++it)
			{
				int r = it->first.first;
				int b = it->first.second;
				double p = it->second;
				if( r>0 ) tgt[rb(r-1,b)] += p * r / (r+b);
				if( b>0 ) tgt[rb(r,b-1)] += p * b / (r+b);
			}
			tmp.swap(tmp2);
		}
	}
};

// BEGIN CUT HERE
#include <ctime>
double start_time; string timer()
 { ostringstream os; os << " (" << int((clock()-start_time)/CLOCKS_PER_SEC*1000) << " msec)"; return os.str(); }
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v)
 { os << "{ ";
   for(typename vector<T>::const_iterator it=v.begin(); it!=v.end(); ++it)
   os << '\"' << *it << '\"' << (it+1==v.end() ? "" : ", "); os << " }"; return os; }
void verify_case(const double& Expected, const double& Received) {
 double diff = Expected - Received; if (diff < 0) diff = -diff; bool ok = (diff < 1e-9);
 if(ok) cerr << "PASSED" << timer() << endl;  else { cerr << "FAILED" << timer() << endl;
 cerr << "\to: \"" << Expected << '\"' << endl << "\tx: \"" << Received << '\"' << endl; } }
#define CASE(N) {cerr << "Test Case #" << N << "..." << flush; start_time=clock();
#define END	 verify_case(_, LastMarble().winningChance(red, blue, removed));}
int main(){

CASE(0)
	int red = 1; 
	int blue = 1; 
	int removed = 0; 
	double _ = 0.5; 
END
CASE(1)
	int red = 1; 
	int blue = 2; 
	int removed = 0; 
	double _ = 0.3333333333333333; 
END
CASE(2)
	int red = 2; 
	int blue = 1; 
	int removed = 0; 
	double _ = 0.6666666666666666; 
END
CASE(3)
	int red = 2; 
	int blue = 2; 
	int removed = 1; 
	double _ = 0.5; 
END
/*
CASE(4)
	int red = ; 
	int blue = ; 
	int removed = ; 
	double _ = ; 
END
CASE(5)
	int red = ; 
	int blue = ; 
	int removed = ; 
	double _ = ; 
END
*/
}
// END CUT HERE
