#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  ll w, h;
  cin >> w >> h;
  int n;
  cin >> n;
  set<int> x, y;
  rep(_, n) {
    int a, b;
    cin >> a >> b;
    x.insert(a);
    y.insert(b);
  }
  ll ans = w * h - (w - x.size()) * (h - y.size()) - n;
  cout << ans << endl;
  return 0;
}