W, H, N = (int(input()) for _ in range(3))
S = set()
K = set()
for _ in range(N):
    s, k = map(int, input().split())
    S.add(s)
    K.add(k)
lS = len(S)
lK = len(K)

print(lS * H + lK * W - lS * lK - N)