using System;
using System.Collections.Generic;
using System.Text;
using sc = Scanner;
using System.Collections;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        Solve();

#if DEBUG
        Console.WriteLine("終了するにはなにかキーを押して下さい...");
        Console.ReadKey();
#endif

    }

    static void Solve()
    {
        long w = sc.NextLong();
        long h = sc.NextLong();
        long n = sc.NextLong();
        int[][] sk = new int[n][];

        for (int i = 0; i < n; i++)
        {
            sk[i] = sc.NextIntArray();
        }
        long answer = 0;
        HashSet<int> wSet = new HashSet<int>();
        HashSet<int> hSet = new HashSet<int>();
        for (int i = 0; i < n; i++)
        {
            if (!wSet.Contains(sk[i][0]))
            {
                wSet.Add(sk[i][0]);
            }
            if (!hSet.Contains(sk[i][1]))
            {
                hSet.Add(sk[i][1]);
            }
        }
        long wFill = (long)wSet.Count;
        long hFill = (long)hSet.Count;
        answer = hFill*w + wFill*(h - hFill) - n;
        Console.WriteLine(answer);

#if DEBUG
        Console.WriteLine("local check"); // Visual Studioのローカル変数チェック用 MainにいくとSolve内のローカル変数消えちゃう
#endif 
    }

 }

public static class Scanner
{
    public static string[] NextStrArray()
    {
        return Console.ReadLine().Split(' ');
    }

    public static long[] NextLongArray()
    {
        string[] s = NextStrArray();
        long[] a = new long[s.Length];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = long.Parse(s[i]);
        }
        return a;
    }
    public static int[] NextIntArray()
    {

        string[] s = NextStrArray();
        int[] a = new int[s.Length];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = int.Parse(s[i]);
        }
        return a;
    }
    public static int NextInt()
    {
        string tmp = "";
        while (true)
        {
            string readData = char.ConvertFromUtf32(Console.Read());
            if (readData == " " || readData == "\n")
                break;
            tmp += readData;
        }
        return int.Parse(tmp);
    }
    public static double NextDouble()
    {
        string tmp = "";
        while (true)
        {
            string readData = char.ConvertFromUtf32(Console.Read());
            if (readData == " " || readData == "\n")
                break;
            tmp += readData;
        }
        return double.Parse(tmp);
    }
    public static long NextLong()
    {
        string tmp = "";
        while (true)
        {
            string readData = char.ConvertFromUtf32(Console.Read());
            if (readData == " " || readData == "\n")
                break;
            tmp += readData;
        }
        return long.Parse(tmp);
    }
    public static double[] NextDoubleArray()
    {

        string[] s = NextStrArray();
        double[] a = new double[s.Length];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = double.Parse(s[i]);
        }
        return a;
    }
}