#include<bits/stdc++.h>

using namespace std;

int main()

{

double r,r1,r2;

cin>>r1>>r2;

r=1/(1/r1+1/r2);

cout<<fixed<<setprecision(2)<<r;

return 0;

}

#include<bits/stdc++.h> using namespace std; int main(){ float r1,r2; cin >> r1 >> r2; cout << fixed<< setprecision(2) << 1 / (1 / r1 + 1 / r2); return 0; }

#include<bits/stdc++.h> using namespace std; int main(){ float r1,r2; cin>>r1>>r2; cout<<fixed<<setprecision(2) <<1 / (1 / r1 +1 / r2); return 0; }