w = int(input())
h = int(input())
n = int(input())

s1 = set()
s2 = set()
for i in range(n):
    s,k = map(int,input().split())
    s1.add(s)
    s2.add(k)

a,b = len(s1),len(s2)
print(a*h+b*w-a*b-n)