#!/usr/bin/env python3
import itertools
import sys

W = int(input())
H = int(input())
N = int(input())
Shand = [False] * (W + 1)
Khand = [False] * (H + 1)
count = 0
Srest = W
Krest = H
Shand = []
Khand = []
for line in sys.stdin:
    S, K = map(int, line.split())
    if S not in Shand:
        Shand.append(S)
        Srest -= 1
    if K not in Khand:
        Khand.append(K)
        Krest -= 1

print(W * H - Srest * Krest - N)