W, H, N = list(map(int, input().split()))

min_x = 0
min_y = 0
max_x = W
max_y = H

for i in range(N):
    x, y, a = list(map(int, input().split()))
    if a == 1:
        min_x = max(min_x, x)
    if a == 2:
        max_x = min(max_x, x)
    if a == 3:
        min_y = max(min_y, y)
    if a == 4:
        max_y = min(max_y, y)

print(max(0, (max_x - min_x)) * max(0, (max_y - min_y)))