w, h, n = map(int, input().split())
coord_list = [list(map(int, input().split())) for i in range(n)]

x_list = [i for i in range(w + 1)]
y_list = [i for i in range(h + 1)]

for a in coord_list:
    if a[-1] == 1:
        x_list = [i for i in x_list if i >= a[0]]
    elif a[-1] == 2:
        x_list = [i for i in x_list if i <= a[0]]
    elif a[-1] == 3:
        y_list = [i for i in y_list if i >= a[1]]
    elif a[-1] == 4:
        y_list = [i for i in y_list if i <= a[1]]

print(max((max(x_list) - min(x_list)), 0) * max((max(y_list) - min(y_list)), 0))