def gridlandMetro(n, m, k, track):
    bins = defaultdict(list)
    # match each track interval to its row
    for t, s, e in track:
        bins[t].append([s, e])
    # initially we have the whole grid available
    ans = m * n
    for b in bins.values():
        # sort the intervals by start time/position
        b.sort()
        gap = 0
        l_bound, r_bound = b[0]
        for i in range(1, len(b)):
            # the intervals overlap - combine them
            if b[i][0] <= r_bound:
                l_bound = min(l_bound, b[i][0])
                r_bound = max(r_bound, b[i][1])
            # the intervals don't overlap - we need to remove space from the grid
            else:
                gap += r_bound - l_bound + 1
                l_bound, r_bound = b[i]
        # the final interval won't be handled in the loop
        gap += r_bound - l_bound + 1
        ans -= gap
        
    return ans