W = int(input())#マークの種類
H = int(input())#数字カードの最大値
N = int(input())
SK = [0 for _ in range(N)]
A = set()
B = set()
for i in range(N):
    a,b = map(int,input().split())
    A.add(a)
    B.add(b)
print(H*W-(W-len(A))*(H-len(B)) - N)