w,h,n=map(int,input().split())


x_min=0
y_min=0

for i in range(n):
    x,y,a=map(int,input().split())

    if a==1:
        x_min=max(x_min,x)

    elif a==2:
        w=min(x,w)

    elif a==3:
        y_min=max(y_min,y)

    elif a==4:
        h=min(y,h)

white=(w-x_min)*(h-y_min)

if white>0:
  print(white)
  
else:
  print("0")