from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline

W = int(input())
H = int(input())
N = int(input())
SK = [tuple(map(int,input().split())) for _ in range(N)]
s = Counter([s for s,k in SK])
k = Counter([k for s,k in SK])
ans = H*W - (W-len(s.values()))*(H-len(k.values()))-N
print(ans)