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

class Magatro
{
    
    static void Main()
    {
        int W = int.Parse(Console.ReadLine());
        int H = int.Parse(Console.ReadLine());
        int N = int.Parse(Console.ReadLine());
        int[] S = new int[N];
        int[] K = new int[N];
        HashSet<int> HashS = new HashSet<int>(),HashK=new HashSet<int>();

        for(int i = 0; i < N; i++)
        {
           int[] q = Console.ReadLine().Split(' ').Select(s=>int.Parse(s)).ToArray();
            HashS.Add(q[0]);
            HashK.Add(q[1]);
            S[i] =q[0];
            K[i] = q[1];
        }
        long All = W * H;
        long scnt = W - HashS.Count;
        long kcnt = H - HashK.Count;
        long cnt = scnt * kcnt + S.Length;
        Console.WriteLine(All - cnt);
    }    

}