A Weird Dragon

We all know about Daenerys Targaryen and her three dragons. And we also know that one of those dragon love’s to eat grass. Recently a farmer of Exile of Essos complained to Daenerys that that dragon ate all grasses of his land. So, Daenerys decided to punish her son I mean that dragon. She will tie that dragon for some time.

Now, the dragon is tied with a rope in a rectangular field. The other end of that rope is in the center of that rectangular field. And the field is full with juicy grass. You are given the length of rope ($R$) and length ($L$) and width ($W$) of rectangular field. Now, the dragon wants you to find out the area ($A$) of this field where he will be able to go and eat grass. You should do this task precisely because you don't want to mess with a grass eating dragon.

Input

There can be several test cases. Each test case contains three integers, $R$ ($1 \le R \le 100000$), $L$ ($1 \le L \le 10000$) and $W$ ($1 \le W \le L$).

Output

You have to print $A$, the required area which is described in the statement. Errors less than $10^{-6}$ will be ignored.

Samples

Input	Output
200 100 80	8000.000000

Input	Output
60 120 100	10409.422430