Problem Description

In an electrical circuit, when resistors with resistance values $ R_1 $ and $ R_2 $ are connected in parallel, the equivalent resistance $ R_3 $ can be determined from the following relationship:

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

Given $ R_1 $ and $ R_2 $, find $ R_3 $.

Input Format

The input is given from the standard input in the following format:

$ R_1 $ $ R_2 $

Output Format

Output the value of $ R_3 $.

The answer will be considered correct if the absolute or relative error is at most $ 10^{-6} $.

Sample Input and Output

Sample Input #1

2 3

Sample Output #1

1.2000000000

Sample Input #2

100 99

Sample Output #2

49.7487437186

Notes/Hints

Constraints

• $1\ \leq\ R_1,\ R_2\ \leq\ 100$
• $R_1,\ R_2$ are integers

见题面 Input 部分

见题面 Output 部分