W = input()
H = input()
N = input()
hand = [tuple(map(int, raw_input().split())) for loop in xrange(N)]

suit = [card[0] for card in hand]
number = [card[1] for card in hand]

w = len(set(suit))
h = len(set(number))

ans = W*H - (W-w)*(H-h) - N
print ans


"""
??
hand.sort()

cnt = 0
suit_hand = set([])
number_hand = set([])
for card in hand:
    if card[0] in suit_hand:
        cnt += W - len(number_hand) - 1
    elif card[1] in suit_hand:
        cnt += H - len(suit_hand) - 1
    else:
        cnt += W - len(number_hand) + H - len(suit_hand) - 2
    suit_hand.add(card[0])
    number_hand.add(card[1])
    print cnt
??
"""