#include <iostream>
#include <vector>
#include <array>
#include <algorithm>
#include <string>
#include <map>
#include <queue>
#include <iomanip>
#include <numeric>
#include <memory>
#include <limits.h>
#include <set>
#include <cassert>
#include <cmath>
#include <bitset>
#include <functional>
#include <limits>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;

#define REP(i,n) for(ll i=0; i<(n); ++i)
#define TEN(x) ((ll)1e##x)
#define ALL(v) (v).begin(), (v).end()

int main(){
	ll w,h,n;
	cin >> w >> h >> n;
	vector<vector<ll>> wh(w);
	set<ll> k_set;
	REP(i, n) {
		ll s, k;
		cin >> s >> k; s--; k--;
		wh[s].push_back(k);
		k_set.insert(k);
	}

	ll c = 0;
	REP(i, w) c += (wh[i].empty()) ? k_set.size() : h - wh[i].size();
	cout << c << endl;
	return 0;
}