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

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