#include <iostream>
#include<cmath>
#include<fstream>



using namespace std;


int main()
{

	int R, x, y;

	double k, a;

	ifstream in("INPUT.txt");
	in >> R >> x >> y;

	if (x<-10||x>10||y<0||y>R||R>10||y>10)
	{
		return 0;
	}

	a = (double)(x*R) / ((R - y) + R);

	k = round(a * 100) / 100;

	ofstream out("OUTPUT.txt");
	out << k;



}