#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i,l,r) for(int i=(int)(l);i<(int)(r);i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)x.size())
template<class T>bool chmax(T &a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T &a,T b){if(a>b){a=b;return 1;}return 0;}

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;

const int inf = 1LL<<60;
const int mod = 1e9 + 7;
const double eps = 1e-9;

/*{
  }*/

signed main(){
  int w, h, n;
  cin >> w >> h >> n;
  
  vi s(n), k(n);
  rep(i, 0, n) cin >> s[i] >> k[i];

  vi c(w), r(h);
  rep(i, 0, n){
    c[s[i]-1]++;
    r[k[i]-1]++;
  }

  int ans = 0, cnt = 0;
  rep(i, 0, w) if(c[i]) ans += h, cnt++;
  ans -= n;
  rep(i, 0, h) if(r[i]) ans += w - cnt;

  cout << ans << endl;

  return 0;
}