#include <sstream>
#include <string>
#include <vector>
#include <map>
#include <algorithm>
#include <iostream>
#include <utility>
#include <set>
#include <cctype>
#include <queue>
#include <stack>
#include <cstdio>
#include <cstdlib>
#include <cmath>

#define INF 1000000000

using namespace std;
typedef long long ll;

int main(void) {
    set<int> w;
    set<int> h;
    int W, H, N;
    cin >> W;
    cin >> H;
    cin >> N;
    ll ans = 0;
    for (int i = 0; i < N; i++) {
        int s, k;
        cin >> s >> k;
        if (w.find(s) == w.end()) {
            ans += H - h.size() - 1;
        }
        if (h.find(k) == h.end()) {
            ans += W - w.size() - 1;
        }
        w.insert(s);
        h.insert(k);
    }
    cout << ans << endl;
    return 0;
}