#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>
using namespace std;
typedef long long LL;
typedef long double LD;
typedef complex<LD> CMP;

class Pillars { public:
	double getExpectedLength(int w, int x, int y)
	{
		if(x>y) swap(x,y);

		double e = 0;
		int num = 1;
		for(int y_minus_x=1-x; y_minus_x<=y-1; ++y_minus_x) {
			e += hypot(y_minus_x, w) * num;
			if(y_minus_x<0)
				++num;
			else if(y_minus_x >= y-x)
				--num;
		}
		return e/y/x;
	}
};

// 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) {
 bool ok = (abs(Expected - Received) < 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(_, Pillars().getExpectedLength(w, x, y));}
int main(){
CASE(0)
	int w = 1; 
	int x = 1; 
	int y = 1; 
	double _ = 1.0; 
END
CASE(1)
	int w = 1; 
	int x = 5; 
	int y = 1; 
	double _ = 2.387132965131785; 
END
CASE(1)
	int w = 1; 
	int x = 1; 
	int y = 5; 
	double _ = 2.387132965131785; 
END
CASE(2)
	int w = 2; 
	int x = 3; 
	int y = 15; 
	double _ = 6.737191281760445; 
END
CASE(2)
	int w = 2; 
	int x = 15; 
	int y = 3; 
	double _ = 6.737191281760445; 
END
CASE(3)
	int w = 10; 
	int x = 15; 
	int y = 23; 
	double _ = 12.988608956320535; 
END
CASE(3)
	int w = 10; 
	int x = 23; 
	int y = 15; 
	double _ = 12.988608956320535; 
END
CASE(4)
	int w = 1000; 
	int x = 100000; 
	int y = 100000; 
	double _ = -1; 
END
CASE(5)
	int w = 1; 
	int x = 1; 
	int y = 1; 
	double _ = 1; 
END

}
// END CUT HERE
