from collections import Counter
W = int(input())
H = int(input())
N = int(input())
S, K = [None] * N, [None] * N
for i in range(N):
    S[i], K[i] = map(str, input().split())
counterS = Counter(S)
counterK = Counter(K)
Wsum = len(counterS)
Hsum = len(counterK)
ans = W * H - (W - Wsum) * (H - Hsum) - N
print(ans)