wuwu, wuwuwu wuwu, wuwuwu wuwu wu

Knight in Corridor
A knight was trapped in a long and narrow corridor . The knight is asked
to travel in the grids from one point and must return this point in the
end. The path he passed will form a polygon; the edges of polygon should
not touch each other. You are asked to compute the maximum area of the
polygon. The following figure shows a series of possible moves of the
knight, the point from A, B, C to D forms a polygon which area is 4.
Note that from a point , the knight can only move to , , , , , , or .

Input:

There are multiple test cases, each case consists of three integer, N, x
and y (x <= N). N is the length of corridor which is not greater
than 1000000000. indicates the starting position of the knight. A test
case with N = 0 indicates the end of input.

Output:

js金沙平台，The maximum area (accurate to two fractional digits) of the polygon in
each line. Assume the side length of grid is 1. If the required polygon
does not exist, output “wuwuwu”.

Sample Input:
4 0 1
4 0 0
0

Sample Output:
4.00
wuwuwu