def main
  w = gets.to_i
  h = gets.to_i
  n = gets.to_i
  w_list = [nil]*(w+1)
  h_list = [nil]*(h+1)
  n.times do
    s,k = gets.split.map(&:to_i)
    w_list[s] = true if w_list[s].nil?
    h_list[k] = true if h_list[k].nil?
  end
  not_used = (w - (w_list.compact!.length)) * (h - (h_list.compact!.length))
  ans = w * h - not_used - n
end

puts main()