#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <cmath>
#include <stack>
#include <algorithm>
#include <iomanip>
#include <map>
#include <queue>
#include <functional>
#include <numeric>
using ll = long long;
using namespace std;

const ll MOD = 1e9 + 7;
ll W, H, N;
// bool operator<(const pair<int, int> &a, const pair<int, int> &b)
// {
//     if (a.first == b.first)
//         return a.second < b.second;
//     return a.first < b.first;
// };

map<ll, ll> mp;
set<ll> st;
int main(void)
{
    cin >> W >> H >> N;
    for (int i = 0; i < N; ++i)
    {
        ll S, K;
        cin >> S >> K;
        st.insert(K);
        mp[S]++;
    }

    ll ans = 0;
    for (auto e : mp)
    {
        ans += H - e.second;
    }
    ans += st.size() * (W - mp.size());
    cout << ans << endl;
    return 0;
}