w = int(input())
h = int(input())
n = int(input())
s = set()
k = set()
for i in range(n):
  si, ki = [int(x) for x in input().split()]
  s.add(si)
  k.add(ki)

sc = len(s)
kc = len(k)
res = 0
res += sc * h
res += kc * (w - sc)
res -= n

print(res)