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

int main() {
    ll W, H, N;
    cin >> W >> H >> N;
    set<ll> s1, s2;
    for (ll i = 0; i < N; i++) {
        ll S, K;
        cin >> S >> K;
        s1.insert(S);
        s2.insert(K);
    }
    cout << H * W - (W - s1.size()) * (H - s2.size()) - N << endl;
}