#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

int main() {
    
    long long W,H,N;
    cin >> W >> H >> N;    
    set<int> S, K;
    for ( int i = 0; i < N; i++ ) {
        int s,k;
        cin >> s >> k;
        S.insert(s); K.insert(k);
    }
    
    cout << S.size()*H + K.size()*W - (S.size()*K.size()) - N << endl;    
    return 0;
}