# coding: utf-8

w, h, N = list(map(int, input().split()))

rect = [0, w, 0, h]
for i in range(N):
    x, y, a = list(map(int, input().split()))
    rect[a - 1] = (lambda c, r, p: [r, c][p * (c - r) < 0])([x, y][a > 2], rect[a - 1], int(not a % 2) - int(a % 2))

length = lambda x: [x, 0][x < 0]
print(length(rect[1] - rect[0]) * length(rect[3] - rect[2]))