using System;
using System.Linq;
using System.Collections.Generic;

namespace yukicoder
{
	class PG
	{
		static void Main(string[] args)
		{
			int W = int.Parse(Console.ReadLine());
			int H = int.Parse(Console.ReadLine());
			int N = int.Parse(Console.ReadLine());
			
			var Wlist = new List<int>();
			var Hlist = new List<int>();
			
			for(int i = 0;i < N;i++)
			{
				var line = Console.ReadLine().Split(' ').Select(c => int.Parse(c)).ToArray();
				
				Wlist.Add(line[0]);
				Hlist.Add(line[1]);
			}
			
			var WDlist = Wlist.Distinct().ToList();
			var HDlist = Hlist.Distinct().ToList();
			
			int Wnum = WDlist.Count;
			int Hnum = HDlist.Count;
			
			Console.WriteLine(Wnum * H + Hnum * W - Wnum * Hnum - N);
		}
	}
}