#include <bits/stdc++.h> 

#define int long long

#define REP(i, b) for(int i = 0; i < (b); i++)
#define REPS(i, b) for(int i = 1; i <= (b); i++)
#define ALL(v) (v).begin(), (v).end()

#define fi first
#define se second
#define pb push_back
#define mp make_pair

using namespace std;

using pi = pair<int, int>;
using vi = vector<int>;
using vs = vector<string>;
using vb = vector<bool>;
using vpi = vector<pi>;
using vvi = vector<vi>;
using vvb = vector<vb>;

const int INF = 1e16;
const int MOD = 1e9+7;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

signed main()
{
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(10);

    int W, H, N; cin >> W >> H >> N;
    set<int> w, h;
    REP(i, N)
    {
        int S, K; cin >> S >> K;
        w.insert(S);
        h.insert(K);
    }
    int n = w.size();
    int m = h.size();
    cout << W*H - (W-n)*(H-m) - N << endl;
}