w = gets.strip.to_i
h = gets.strip.to_i
n = gets.strip.to_i
cards = []
n.times do
	card = gets.strip.split(' ').map(&:to_i)	
	cards << card
end
set_s = []
set_k = []
cards.each do |card|
	set_s << card[0]
	set_k << card[1]
end
set_s.uniq!
set_k.uniq!

count = set_s.length * h + set_k.length * w - set_s.length * set_k.length - cards.length
p count