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

left = 0
right = W
bottom = 0
top = H

for i in range(N):
  x, y, a = map(int, input().split())
  if a == 1:
    left = max(left, x)
  elif a == 2:
    right = min(right, x)
  elif a == 3:
    bottom = max(bottom, y)
  else:
    top = min(top, y)
    
print((right-left) * (top-bottom))