#include<bits/stdc++.h>
using namespace std;
int main() {
    double r1,r2;
    cin>>r1>>r2;
    printf("%.2f",1/(1/r1+1/r2));
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main(){
    char a;
    cin>>a;
    cout<<"  "<<a<<endl;
    cout<<" "<<a<<a<<a<<endl;
    cout<<a<<a<<a<<a<<a<<endl;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main(){
	char s;
	cin >> s;
	cout << "  " << s <<endl;
	cout << " " << s << s << s << endl;
	cout << s << s << s << s << s ;
    return 0; 
}

#include<bits/stdc++.h> using namespace std; int main(){ char x; cin>>x; cout<<" "<<x<<" "<<endl; cout<<" "<<x<<x<<x<<" "<<endl; cout<<x<<x<<x<<x<<x<<endl; return 0; }