#include<bits/stdc++.h>
using namespace std;
using ll = long long;

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    ll W, H, N;
    cin >> W >> H >> N;
    
    set<ll> se0;
    set<ll> se1;

    FOR(i, 0, N){
        ll s, k;
        cin >> s >> k;

        se0.insert(s);
        se1.insert(k);
    }

    ll w = se0.size();
    ll h = se1.size();

    ll sum = w*H + h*W - h*w - N;
    p(sum);
    
    return 0;
}