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

using i64 = long long;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);

    auto solve = [&]() {
        int w, h, n;
        cin >> w >> h >> n;

        set<int> x, y;
        for (int i = 0; i < n; i++) {
            int a, b;
            cin >> a >> b;
            x.insert(a), y.insert(b);
        }

        i64 ans = 1LL * w * h - 1LL * (w - x.size()) * (h - y.size()) - n;
        cout << ans << '\n';
    };
    
    solve();
    
    return 0;
}