W, H, N = map(int, input().split())
w = 0
h = 0
lx = list()
ly = list()
la = list()
for i in range(1, N+1):
    X, Y, A = map(int, input().split())
    lx.append(X)
    ly.append(Y)
    la.append(A)
    if A == 1 and w < X:
        w = X
    elif A == 2 and X < W:
        W = X
    elif A == 3 and h < Y:
        h = Y
    elif A == 4 and Y < H:
        H = Y
S = (W - w)*(H - h)
if S < 0:
    S = 0
print(S)