Tallying is done manually in the presence of representatives of all contesting parties. Party tallying, which is easier, is done first so that returns may be announced quickly. Individual candidate tallying is done next and can take several days. Once the number of seats per party and constituency is determined, the seats are filled on a top-down basis from the individual cross-of-preference tallies. Party heads and acting or past Prime Ministers are exempt from cross-of-preference voting: they are automatically placed at the top of their party list and are elected, provided their party achieves at least one seat in the particular constituency.