#include <bits/stdc++.h>
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define FORR(i,a,b) for (int i=(a);i>=(b);i--)
#define pb push_back

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef set<int> si;
const int inf = 1e9;
const int mod = 1e9+7;

ll w, h, n, s, k;
set<ll> sw, sh;
main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> w >> h >> n;
  FOR(i, 0, n){
    cin >> s >> k;
    sw.insert(s);
    sh.insert(k);
  }
  cout << w * h - (w - sw.size())*(h - sh.size()) - n << endl;
}