w, h, n = map(int, input().split())
nums_list=[list(map(int, input().split())) for i in range(n)]
minX = 0
maxX = w
minY = 0
maxY = h
for nums in nums_list:
	x, y, a = map(int, nums)
	if a == 1:
		minX = minX if (minX > x) else x
	elif a == 2:
		maxX = maxX if (maxX < x) else x
	elif a == 3:
		minY = minY if (minY > y) else y
	elif a == 4:
		maxY = maxY if (maxY < y) else y
width = maxX-minX if (maxX-minX > 0) else 0
height = maxY-minY if (maxY-minY > 0) else 0
v = width*height
print(v)