using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace yukicoder
{
    class _011
    {
        static void Main()
        {
            int w = int.Parse(Console.ReadLine());
            int h = int.Parse(Console.ReadLine());
            int n = int.Parse(Console.ReadLine());

            int[][] skn = new int[n][];
            for (int i = 0; i < n; i++)
            {
                skn[i] = Array.ConvertAll(Console.ReadLine().Split(' ')
                , x => int.Parse(x));
            }

            int ans = 0;
            HashSet<int> tw = new HashSet<int>();
            HashSet<int> th = new HashSet<int>();
            for (int i = 0; i < n; i++)
            {
                int sn = skn[i][0] - 1;
                int kn = skn[i][1] - 1;

                if (tw.Contains(sn) && th.Contains(kn))
                {
                    ans--;
                    continue;
                }
                if (!tw.Contains(sn))
                {
                    ans += h - th.Count - 1;
                }

                if (!th.Contains(kn))
                {
                    ans += w - tw.Count - 1;
                }
                tw.Add(sn);
                th.Add(kn);
            }
            Console.WriteLine(ans);
        }
    }
}