Problems
Average train speed
Average train speed
Find the average speed of the train, if it traveled the first half of the distance at a speed of $v_1$, and the second half at a speed of $v_2$.
\InputFile
Two integers $v_1$ and $v_2~(1 \le v_1, v_2 \le 10^9)$.
\OutputFile
Print the average speed of the train with $4$ decimal places.
Input example #1
10 10
Output example #1
10.0000
Input example #2
50 100
Output example #2
66.6667