#include "bits/stdc++.h"
using namespace std;
#define ll long long int
#define rep(i,n) for( int i = 0; i < n; i++ )
#define rrep(i,n) for( int i = n; i >= 0; i-- )
#define REP(i,s,t) for( int i = s; i <= t; i++ )
#define RREP(i,s,t) for( int i = s; i >= t; i-- )
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define INF 2000000000
#define mod 1000000007
#define INF2 1000000000000000000
#define int long long

signed main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);
	int H, W;
	cin >> H >> W;
	set<int> st1;
	set<int> st2;
	int N; cin >> N;
	rep(i, N) {
		int a, b;
		cin >> a >> b;
		st1.insert(a);
		st2.insert(b);
	}
	int kind1 = st1.size();
	int kind2 = st2.size();
	cout << kind1 * W + kind2 * H - kind1 * kind2 - N << endl;

    return 0;
}