#include <bits/stdc++.h>

using namespace std;

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

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int w, h, n;
set<int> spat, snum;

int main() {
	cin >> w >> h >> n;
	REP(i, n) {
		int s, k;
		scanf("%d %d", &s, &k);
		spat.insert(s);
		snum.insert(k);
	}
	
	ll ans = (ll)spat.size() * h + (ll)snum.size() * (w - spat.size());
	ans -= n;
	
	cout << ans << endl;
	return 0;
}