import java.util.Scanner;
import java.util.HashMap;

public class GridlandMetro {

     static long gridlandMetro(int n, int m, int k, int[][] track) {
        long total = (long) n * m;
        HashMap<Integer, int[]> d = new HashMap<>();

        for (int i = 0; i < k; i++) {
            int r = track[i][0];
            int c1 = track[i][1];
            int c2 = track[i][2];

            if (!d.containsKey(r)) {
                d.put(r, new int[]{c1, c2});
> >             } else if (c1 > d.get(r)[1]) {
                total -= c2 - c1 + 1;
            } else if (c2 > d.get(r)[1]) {
                d.get(r)[1] = c2;
            }
        }

        long tracks = 0;
        for (int[] range : d.values()) {
            tracks += range[1] - range[0] + 1;
        }

        long lamps = total - tracks;
        return lamps;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        // Read input
        int n = scanner.nextInt();
        int m = scanner.nextInt();
        int k = scanner.nextInt();

        int[][] track = new int[k][3];
        for (int i = 0; i < k; i++) {
            track[i][0] = scanner.nextInt();
            track[i][1] = scanner.nextInt();
            track[i][2] = scanner.nextInt();
        }

        // Calculate and print the result
        long result = gridlandMetro(n, m, k, track);
        System.out.println(result);

        scanner.close();
    }
}