/* -*- coding: utf-8 -*-
 *
 * 11.cc: No.11 カードマッチ - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100;

/* typedef */

typedef long long ll;
typedef set<int> si;

/* global variables */

/* subroutines */

/* main */

int main() {
  ll w, h;
  int n;
  cin >> w >> h >> n;

  si xset, yset;
  for (int i = 0; i < n; i++) {
    int xi, yi;
    cin >> xi >> yi;
    xset.insert(xi);
    yset.insert(yi);
  }

  int xn = xset.size(), yn = yset.size();
  ll ans = h * xn + w * yn - xn * yn - n;
  printf("%lld\n", ans);
  return 0;
}