#include <iostream>
#include <vector>

int main() {
    using namespace std;
    int w, h, n;
    cin >> w >> h >> n;
    vector<bool> row(h, false), col(w, false);
    for (int _ = 0; _ < n; _++) {
        int s, k;
        cin >> s >> k;
        row[k - 1] = true;
        col[s - 1] = true;
    }
    long long cnt_row = 0, cnt_col = 0;
    for (int i = 0; i < h; i++) {
        if (row[i]) { cnt_row++; }
    }
    for (int i = 0; i < w; i++) {
        if (col[i]) { cnt_col++; }
    }
    long long ans = cnt_row * w + cnt_col * h - cnt_row * cnt_col - n;
    cout << ans << endl;
}