#include<iostream>
#include<algorithm>
#include<stack>
#include<queue>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<string>
using namespace std;
int main(){	
	double r1,r2;
	cin >> r1 >> r2;
	double r = 1.0/(1.0/r1+1.0/r2);
	printf("%.2lf",r);
	return 0;
} 

#include<bits/stdc++.h>
#define up(l,r,i) for(int i=l,END##i=r;i<=END##i;++i)
#define dn(r,l,i) for(int i=r,END##i=l;i>=END##i;--i)
using namespace std;
typedef long long i64;
const int INF =2147483647;
double a,b;
int main(){
    scanf("%lf%lf",&a,&b);
    printf("%.2lf\n",1.0/(1.0/a+1.0/b));
    return 0;
}

#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;
}