using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var W = sc.ReadInt();
        var H = sc.ReadInt();
        var N = sc.ReadInt();

        var l = 0;
        var r = W;
        var b = 0;
        var t = H;
        for (int i = 0; i < N; i++)
        {
            var x = sc.ReadInt();
            var y = sc.ReadInt();
            var a = sc.ReadInt();
            switch (a)
            {
                case 1:
                    l = Math.Max(l, x);
                    break;
                case 2:
                    r = Math.Min(r, x);
                    break;
                case 3:
                    b = Math.Max(b, y);
                    break;
                case 4:
                    t = Math.Min(t, y);
                    break;
            }
        }
        if (r - l < 0 || t - b < 0)
        {
            Console.WriteLine(0);
        }
        else
        {
            var ans = (r - l) * (t - b);
            Console.WriteLine(ans);
        }
    }

    static int MOD = (int)1e9 + 7;
    static int INF = (int)1e7 + 1;
    static long LINF = (long)1e13 + 1;
    static Scanner sc = new Scanner();
}

class Scanner
{
    string[] S = new string[0];
    int Index = 0;
    char[] Separators = new char[] { ' ' };

    public string Next()
    {
        if (this.Index < this.S.Length) return this.S[this.Index++];
        var line = "";
        while (line == "") line = Console.ReadLine();
        this.S = line.Split(this.Separators, StringSplitOptions.RemoveEmptyEntries);
        if (this.S.Length == 0) return this.Next();
        this.Index = 0;
        return this.S[this.Index++];
    }
    public string ReadStr()
    {
        return this.Next();
    }
    public char ReadChar()
    {
        return this.Next()[0];
    }
    public int ReadInt()
    {
        return int.Parse(this.Next());
    }
    public uint ReadUInt()
    {
        return uint.Parse(this.Next());
    }
    public long ReadLong()
    {
        return long.Parse(this.Next());
    }
    public double ReadDouble()
    {
        return double.Parse(this.Next());
    }
    public int[] ReadIntArray(int n)
    {
        var array = new int[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadInt();
        }
        return array;
    }
    public long[] ReadLongArray(int n)
    {
        var array = new long[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadLong();
        }
        return array;
    }
    public double[] ReadDoubleArray(int n)
    {
        var array = new double[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadDouble();
        }
        return array;
    }
    public char[] ReadCharArray(int n)
    {
        var array = new char[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadChar();
        }
        return array;
    }
    public string[] ReadStrArray(int n)
    {
        var array = new string[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadStr();
        }
        return array;
    }
}


Measured memory_bytes: 11092