Score : 100 points
There is a right triangle ABC with ∠ABC=90°.
Given the lengths of the three sides, |AB|,|BC| and |CA|, find the area of the right triangle ABC.
It is guaranteed that the area of the triangle ABC is an integer.
Input is given from Standard Input in the following format:
|AB| |BC| |CA|
Print the area of the triangle ABC.
3 4 5
6
This triangle has an area of 6.
5 12 13
30
This triangle has an area of 30.
45 28 53
630
This triangle has an area of 630.