Tudor, having finally had his fill of tea, now needs to think about keeping his goats safe.

Tudor has obtained a large rectangular door that is ~X~ metres long, ~Y~ metres high, and 1 metre thick. He intends on using this door to gate access to his goats.

There's only one problem - having just one door is aesthetically unpleasing to Tudor.

Therefore, he intends on taking the door and cutting it in half to make a set of double doors that he can use to gate access to his goats.

After cutting the door in half, what is the volume of one of the doors?

Constraints

~1 \le X, Y \le 10^9~

In tests worth 14 marks, ~\max(X, Y) \le 10~.

Input Specification

The input will consist of two positive space separated integers, ~X~ and ~Y~.

Output Specification

Output, on a single line, the volume of one of the doors. The volume must be printed with exactly one digit after the decimal point.

Sample Input

2 2

Sample Output

2.0