#include <iostream>
#include <string>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <vector>
#include <cmath>
#include <cstdlib>
#include <queue>
#include <stack>
#include <iomanip>

using namespace std;

#define REP(i, n) for(ll i = 0;i < n;i++)
#define REPR(i, n) for(ll i = n;i >= 0;i--)
#define FOR(i, m, n) for(ll i = m;i < n;i++)
#define FORR(i, m, n) for(ll i = m;i >= n;i--)
#define REPO(i, n) for(ll i = 1;i <= n;i++)
#define ll long long
#define INF (ll)1 << 60
#define MINF (-1 * INF)
#define ALL(n) n.begin(),n.end()
#define MOD 1000000007
#define P pair<ll, ll>

ll a, b, n, s1[110], s2[110];
set<pair<ll, ll>> se;
int main() {
	cin >> a >> b >> n;
	REP(i, n)cin >> s1[i] >> s2[i];
	REP(i, n) {
		REPO(j, a)se.insert(P(j, s2[i]));
		REPO(j, b)se.insert(P(s1[i], j));
	}
	cout << se.size() - n << endl;
}