Triangle Area

Per-Magnus managed to solve his addition homework thanks to you, but now he is unfortunately posed with an even greater problem.

He has been given a triangular cake by his mother, and wonders what the area of it is. It turns out Per-Magnus forgot the formula for computing it!

Per-Magnus managed to measure the base and height of the triangle with a ruler. Given this, compute the area of the triangular cake.

Input

The input consists of a single line with two integers $ 1 \le h \le 1000 $ and $1 \le b \le 1000$, the height and base of the triangle.

Output

Output a single number, the area of the triangle. Your answer must be correct within an absolute or relative error of $10^{-7}$.

Sample Input 1 Sample Output 1
1 1
0.5
Sample Input 2 Sample Output 2
2 2
2