from collections import defaultdict

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

mark = defaultdict(int)
mark_set = set()
num = defaultdict(int)
num_set = set()
ans = 0
for i in range(n):
    s, k = map(int, input().split())
    mark[s] += 1
    num[k] += 1
    mark_set.add(s)
    num_set.add(k)
ans += (len(mark_set) * h) + (len(num_set) * w ) - (len(mark_set) * len(num_set)) - n
print(ans)