#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(){
    double r1,r2;
    cin>>r1>>r2;
    double R=1/((1/r1)+(1/r2));
    cout<<fixed<<setprecision(2)<<R;
    return 0;
}

using namespace std;
int main()
{
	srand(time(NULL));
	cout<<rand();
	return 0;
}