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

min_x=0
min_y=0

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

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

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

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

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

white=int((w-min_x)*(h-min_y))

if white>0:
    print(white)

else:
    print("0")
