class Calc0011
  def initialize(args)
    args = args.map { |l| l.chomp.split(/\s+/) }
    @w = args.shift.first.to_i
    @h = args.shift.first.to_i
    @n = args.shift.first.to_i
    @cards = args.map { |l| l.map(&:to_i) }
  end

  def run
    ws = @cards.map(&:first).uniq.size
    hs = @cards.map(&:last).uniq.size
    ws * @h + hs * @w - ws * hs - @cards.size
  end
end

puts Calc0011.new(STDIN.readlines).run if __FILE__ == $0