#include<bits/stdc++.h>
using namespace std;
int main()
{
	double ab,a,b,t;
	cin>>ab>>a>>b;
	t=ab/(a+b/2+a/2)*(b/2+a/2)/b+ab/(a+b/2+a/2);
	cout<<fixed<<setprecision(6)<<t<<endl;
	return 0;
}