W, H, N = map(int, input().split())
X, Y = 0, 0
for i in range(N):
  x, y, a = map(int, input().split())
  if a == 1:
    X = max(x, X)
  elif a == 2:
    W = min(W, x)
  elif a == 3:
    Y = max(y, Y)
  elif a == 4:
    H = min(H, y)
ans = (W-X)*(H-Y)
if ans <= 0:
  print(0)
else:
  print(ans)
