using System;
using System.Collections.Generic;

namespace No11{
    public class Program{
        public static void Main(string[] args){
            var sr = new StreamReader();
            //---------------------------------
            var W = sr.Next<int>();
            var H = sr.Next<int>();
            var N = sr.Next<int>();

            var hsw = new HashSet<int>();
            var hsh = new HashSet<int>();
            for(var i = 0; i < N; i++){
                hsw.Add(sr.Next<int>());
                hsh.Add(sr.Next<int>());
            }

            Console.WriteLine(hsw.Count * H + hsh.Count * W - hsw.Count * hsh.Count - N);
            //---------------------------------
        }
    }

    public class StreamReader{
        private readonly char[] _c = {' '};
        private int _index = -1;
        private string[] _input = new string[0];

        public T Next<T>(){
            if(_index == _input.Length - 1){
                _index = -1;
                while(true){
                    string rl = Console.ReadLine();
                    if(rl == null){
                        if(typeof(T).IsClass) return default(T);
                        return (T)typeof(T).GetField("MinValue").GetValue(null);
                    }
                    if(rl != ""){
                        _input = rl.Split(_c, StringSplitOptions.RemoveEmptyEntries);
                        break;
                    }
                }
            }
            return (T)Convert.ChangeType(_input[++_index], typeof(T), System.Globalization.CultureInfo.InvariantCulture);
        }
    }
}