Problem:
Score : 100 points

Problem Statement

In an electric circuit, when two resistors R_1 and R_2 are connected in parallel, the equivalent resistance R_3 can be derived from the following formula:

\frac{1}{R_1} + \frac{1}{R_2} = \frac{1}{R_3}

Given R_1 and R_2, find R_3.

Constraints

1 \leq R_1, R_2 \leq 100

R_1 and R_2 are integers.

Input

The input is given from Standard Input in the following format:

R_1 R_2

Output

Print the value of R_3.

The output is considered correct if the absolute or relative error is at most 10^{-6}.

Sample Input 1

2 3

Sample Output 1

1.2000000000

Sample Input 2

100 99

Sample Output 2

49.7487437186

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

 
#include <bits/stdc++.h>
using namespace std;
using vi=vector<int>;
using vvi=vector<vi>;
using vs=vector<string>;
using msi=map<string,int>;
using mii=map<int,int>;
using pii=pair<int,int>;
using vlai=valarray<int>;
using ll=long long;
#define rep(i,n) for(int i=0;i<n;i++)
#define range(i,s,n) for(int i=s;i<n;i++)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define fs first
#define sc second
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define INF 1e9
#define EPS 1e-9
constexpr int gcd(int a,int b){return b?gcd(b,a%b):a;}
constexpr int lcm(int a,int b){return a*b/gcd(a,b);}


int main(){
    double a,b;cin>>a>>b;
    cout<<fixed<<setprecision(10)<<(a*b)/(a+b)<<endl;
	return 0;
}