#include <iostream>
#include <algorithm>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>
#include <limits>

static const int MOD = 998244353;
using ll = long long;
using uint = unsigned;
using ull = unsigned long long;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max() / 32 * 15 + 208;

template <typename T>
using GPQ = priority_queue<T, vector<T>, greater<T>>;

int main() {
    ll w, h, n;
    cin >> w >> h >> n;
    map<int, int> a, b;
    for (int i = 0; i < n; ++i) {
        int p, q;
        cin >> p >> q;
        a[p]++;
        b[q]++;
    }
    cout << w*h-(w-a.size())*(h-b.size())-n << "\n";
    return 0;
}