With hashing function f(x) = x & (2^16 - 1), we get AC if we assume that no two different x have the same hash, which, obviously, is wrong.
UPD: Even worse, 2^15 - 1 works as well.

Edited by author 07.10.2009 03:21

They can't make test for every hash func. You use 2^16-1, I use -2 or mod 500000 etc, how can they figure out those all?