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 Rust (1.42.0) (judge verdict: Accepted)

fn main(){
    let r: Vec<f64> = read_vec();
    println!("{:.10}", r[0] * r[1] / (r[0] + r[1]));
}

#[allow(dead_code)]
fn read_vec<T>() -> Vec<T>
where T: std::str::FromStr,
      T::Err: std::fmt::Debug
{
    let mut buf = String::new();
    std::io::stdin().read_line(&mut buf).expect("failed to read");
    buf.split_whitespace().map(|e| e.parse().unwrap()).collect()
}