#include #include using namespace std; int main () { double x,y,R; cin>>x>>y; R=(x*y)/(x+y); cout<<fixed<<setprecision(2)<<R<<endl; return 0; }

#include<bits/stdc++.h>
using namespace std;
int main()
{
	double a,b;
	cin>>a>>b;
	cout<<fixed<<setprecision(2)<<1/(1/a+1/b);
	return 0;
}