W, H, N = map(int, input().split())
P = [list(map(int, input().split())) for _ in range(N)]
X1, X2, Y1, Y2 = 0, W, 0, H

for x, y, a in P:
    if a == 1:
        X1 = max(X1, x)
    elif a == 2:
        X2 = min(X2, x)
    elif a == 3:
        Y1 = max(Y1, y)
    elif a == 4:
        Y2 = min(Y2, y)

if X2 <= X1 or Y2 <= Y1:
    S = 0
else:
    S = (X2 - X1) * (Y2 - Y1)

print(S)