using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using Enu = System.Linq.Enumerable;

class Program
{
    void Solve()
    {
        int NumSuit = reader.Int(), MaxNum = reader.Int();
        int N = reader.Int();
        var C = reader.IntGrid(N);
        Console.WriteLine(Naive(NumSuit, MaxNum, C));

        //var suit = new Dictionary<int, HashSet<int>>();
        //var num = new Dictionary<int, HashSet<int>>();

        //foreach (var a in C)
        //{
        //    Add(suit, a[0], a[1]);
        //    Add(num, a[1], a[0]);
        //}
        //foreach (int s in suit.Keys)
        //    foreach (int n in suit[s])
        //        foreach (int numKey in num.Keys)
        //            num[numKey].Add(s);

        //int ans = 0;
        //ans += suit.Values.Sum(s => MaxNum - s.Count);
        //ans += num.Values.Sum(s => NumSuit - s.Count);

        //Console.WriteLine(ans);
        //Console.ReadLine();
    }

    void Add(Dictionary<int, HashSet<int>> dic, int key, int val)
    {
        if (!dic.ContainsKey(key)) dic[key] = new HashSet<int>();
        dic[key].Add(val);
    }

    int Naive(int NumSuit, int MaxNum, int[][] C)
    {
        var set = new HashSet<long>();
        Func<int, int, long> Key = (suit, num) => suit * (long)1e10 + num;

        foreach (var a in C)
        {
            for (int n = 1; n <= MaxNum; n++) set.Add(Key(a[0], n));
            for (int s = 1; s <= NumSuit; s++) set.Add(Key(s, a[1]));
        }
        foreach (var a in C)
            set.Remove(Key(a[0], a[1]));

        return set.Count;
    }




    Reader reader = new Reader(Console.In);
    static void Main() { new Program().Solve(); }
}

class Reader
{
    private readonly TextReader reader;
    private readonly char[] separator = { ' ' };
    private readonly StringSplitOptions removeOp = StringSplitOptions.RemoveEmptyEntries;
    private string[] A = new string[0];
    private int i;

    public Reader(TextReader r) { reader = r; }
    public bool HasNext() { return Enqueue(); }
    public string String() { return Dequeue(); }
    public int Int() { return int.Parse(Dequeue()); }
    public long Long() { return long.Parse(Dequeue()); }
    public double Double() { return double.Parse(Dequeue()); }
    public int[] IntLine() { var s = Line(); return s == "" ? new int[0] : Array.ConvertAll(Split(s), int.Parse); }
    public int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); }
    public int[][] IntGrid(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); }
    public string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Line()).ToArray(); }
    public string Line() { return reader.ReadLine().Trim(); }
    private string[] Split(string s) { return s.Split(separator, removeOp); }
    private bool Enqueue()
    {
        if (i < A.Length) return true;
        string line = reader.ReadLine();
        if (line == null) return false;
        if (line == "") return Enqueue();
        A = Split(line);
        i = 0;
        return true;
    }
    private string Dequeue() { Enqueue(); return A[i++]; }
}