w = gets.to_i
h = gets.to_i
n = gets.to_i
t = []
n.times do 
  t.push(gets.chomp.split(" ").map(&:to_i))
end
a = 0
m = []
mm = []
w.times do |d|
  p = h - t.map{|u|u[0]}.count(d+1)
  unless(p == h) 
    a += p 
    m.push(d)
    mm.push(t.map{|u|u[1]})
  end 
end
m.uniq!
mm = mm.flatten.uniq
a += mm.size * (w - m.size) 
p a