#include<iostream>
#include<iomanip>
#include<string>
#include<algorithm>
#include<vector>
#include<set>
#include<list>
#include<queue>
#include<math.h>
#include<bitset>
using ll = long long;
using namespace std;

int main(){
    int w, h, n;
    ll ans = 0;
    cin >> w >> h >> n;
    int suit_n = w, num_n = h;
    set<int> suit, num;
    for (int i = 0; i < n; i++){
        int s, k;
        cin >> s >> k;
        suit.insert(s);
        num.insert(k);
    }

    cout << w*h - (w-suit.size())*(h-num.size()) - n << endl;
}