W,H,N=map(int,input().split())
x1=0
x2=W
y1=0
y2=H
for i in range(N):
    x,y,a=map(int,input().split())
    if a==1:
        x1=max(x1,x)
    elif a==2:
        x2=min(x,x2)
    elif a==3:
        y1=max(y1,y)
    elif a==4:
        y2=min(y,y2)
if x2<x1 or y2<y1:
    print(0)
    exit()
xx=x2-x1
yy=y2-y1
print(xx*yy)