#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

long long solve_vertical(vector<int> a, int x) {
    sort(a.begin(), a.end());
    int n = a.size();
    long long result = a[n - 1] - a[0];
    for (int i = 1; i < n; ++i) {
        long long possible = (x + a[i - 1]) - a[i];
        result = min(result, possible);
    }
    return result + 1;
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int h, w, n;
    cin >> h >> w >> n;
    vector<int> r(n), c(n);
    for (int i = 0; i < n; ++i) {
        cin >> r[i] >> c[i];
    }

    cout << solve_vertical(r, h) * solve_vertical(c, w) << '\n';
}