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

namespace yukicoder
{
	public class Program
	{
		public static void Main()
		{
			var h = int.Parse(Console.ReadLine());
			var w = int.Parse(Console.ReadLine());
			var n = int.Parse(Console.ReadLine());
			var s = new int[n];
			var k = new int[n];
			for(var i= 0; i < n; i++)
            {
				var a = Console.ReadLine().Split(' ').Select(value => int.Parse(value) - 1).ToArray();
				s[i] = a[0];
				k[i] = a[1];
			}
			var ss = s.Distinct();
			var kk = k.Distinct();
			Console.WriteLine(h * w - (w - kk.Count()) * (h - ss.Count()) - n);
        }
    }
}