W,H,N = int(raw_input()),int(raw_input()),int(raw_input()) S,K = [0 for i in range(N)],[0 for i in range(N)] for i in range(N): S[i],K[i] = map(int,raw_input().split()) S,K = set(S),set(K) ans = W * H - (W - len(S)) * (H - len(K)) ans -= N print ans