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

#include <iostream>
#include <iomanip>
using namespace std;
float r1,r2;
int main()
{
	cin >> r1 >> r2;
	cout << fixed << setprecision(2) << 1.0 / (1 / r1 + 1 / r2);
	return 0;
 }

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