#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
#define MOD 1000000007
#define INF 100000000
using namespace std;
typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PI;


int main() {
	int w, h;
	LL n;
	cin >> w >> h >> n;
	LL ans = w * h - n;
	set<int> ss, ks;
	REP(i, n) {
		int s, k;
		cin >> s >> k;
		ss.insert(s);
		ks.insert(k);
	}
	ans = ans - (w - ss.size()) * (h - ks.size());
	cout << ans << endl;
	return 0;
}