#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <functional>
#include <tuple>
#include <climits>
#include <algorithm>
#include <queue>
#include <unordered_map>
#include <unordered_set>
#include <set>
#include <iomanip>

using namespace std;

int main()
{
    int W, H, N;
    cin >> W >> H >> N;
    vector<int> S(N), K(N);
    set<tuple<int, int>> hand;
    set<tuple<int, int>> match;
    enum {
        suit = 0,
        number = 1
    };
    for(int i=0; i<N; i++) {
        cin >> S[i] >> K[i];
        hand.insert(make_tuple(S[i], K[i]));
    }
    for(const auto &h : hand) {
        for(int i=1; i<=W; i++) {
            if(hand.count(make_tuple(i, get<number>(h))) == 0) {
                match.insert(make_tuple(i, get<number>(h)));
            } 
        }
        for(int i=1; i<=H; i++) {
            if(hand.count(make_tuple(get<suit>(h), i)) == 0) {
                match.insert(make_tuple(get<suit>(h), i));
            }
        }
    }
    cout << match.size() << endl;
}