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

points = [list(map(int, input().split())) for _ in range(N)]
res = 0

x1,y1 = [0,0]
x2,y2 = [W,H]

for x,y,a in points:
    if a == 1:
        x1 = max(x1, x)
    if a == 2:
        x2 = min(x2, x)
    if a == 3:
        y1 = max(y1, y)
    if a == 4:
        y2 = min(y2, y)

if x2-x1 <= 0 or y-y1 <=0:
    print(0)
else:
    res = (x2-x1) * (y2 - y1)
    print(res)