#include<bits/stdc++.h>
#define yy return 0;
using namespace std;
double a,b;
int main() { cin>>a>>b;printf("%.2lf",1.0/(1.0/a+1.0/b));yy
}

#include<bits/stdc++.h> #define yy return 0; using namespace std; double a,b; int main() { cin>>a>>b;printf("%.2lf",1.0/(1.0/a+1.0/b));yy }

#include<iostream>
#include<iomanip>
using namespace std;
int main(){
    double a,b,R;
    cin>>a>>b;
    R=1/(1/a+1/b);
    cout<<fixed<<setprecision(2)<<R;
    return 0;
}