#include<iostream>
#include<iomanip>
#include<cmath>
#include<bits/stdc++.h>
#include<cstdio>
#include <stdio.h>
using namespace std;
int main( )
{
double r1,r2;
cin>>r1>>r2;
cout<<fixed<<setprecision(6)<<1/(1/r1+1/r2);

return 0;
}