import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		try {

			int max_x = sc.nextInt();
			int max_y = sc.nextInt();
			int n = sc.nextInt();

			int min_x = 0;
			int min_y = 0;

			for (int i = 0; i < n; i++) {

				int x = sc.nextInt();
				int y = sc.nextInt();
				int a = sc.nextInt();

				if (a == 1) {
					if (min_x < x) {
						min_x = x;
					}
				}
				else if (a == 2) {
					if (x < max_x) {
						max_x = x;
					}
				}
				else if (a == 3) {
					if (min_y < y) {
						min_y = y;
					}
				}
				else if (a == 4) {
					if (y < max_y) {
						max_y = y;
					}
				}
			}

			if (max_x <= min_x || max_y <= min_y) {
				System.out.println(0);
			}
			else {
				System.out.println((max_x - min_x) * (max_y - min_y));
			}
		}
		finally {
			sc.close();
		}
	}

}