W, H, N = [int(x) for x in input().strip().split()]
x_min = 0
y_min = 0

for i in range(N):
    x, y, a = [int(x) for x in input().strip().split()]
    result = 0
    if W < x_min or H < y_min:
        W - x_min == 0
        continue

    if a == 1 and x_min < x:
        x_min = x
    elif a == 2 and W > x:
        W = x
    elif a == 3 and y_min < y:
        y_min = y
    elif a == 4 and H > y:
        H = y
    
print((W - x_min)*(H - y_min))