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

#include<bits/stdc++.h>
using namespace std;
int main(){
    double a,b;
    cin>>a>>b;
    cout<<fixed<<setprecision(9)<<a/b;
}

#include<bits/stdc++.h>
using namespace std;
int main(){
    double a,b;
    cin>>a>>b;
    cout<<fixed<<setprecision(9)<<a/b;
}