import sys
W,H,N=map(int,input().split())
wide=[0,W]
height=[0,H]
# white sphere calculate
for i in range(N):
    x,y,a=map(int,input().split())
    if a==1:
        wide[0]=max(wide[0],x)
    elif a==2:
        wide[1]=min(wide[1],x)
    elif a==3:
        height[0]=max(height[0],y)
    elif a==4:
        height[1]=min(height[1],y)
w_len=wide[1]-wide[0]
h_len=height[1]-height[0]
s=w_len*h_len
if h_len<0 or w_len<0:
    print(0)
else:
    print(s)