#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;
} 

#include<bits/stdc++.h> using namespace std;

int main(){ float r1,r2; cin>>r1>>r2; cout<<fixed<<setprecision(2)<<1/((1/r1)+(1/r2)); return 0; }

#include<bits/stdc++.h>
using namespace std;

int main(){
	float r1,r2;
	cin>>r1>>r2;
	cout<<fixed<<setprecision(2)<<1/((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;
}