#include <iostream>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>	// require sort next_permutation count __gcd reverse etc.
#include <cstdlib>	// require abs exit atof atoi 
#include <cstdio>		// require scanf printf
#include <functional>
#include <numeric>	// require accumulate
#include <cmath>		// require fabs
#include <climits>
#include <limits>
#include <cfloat>
#include <iomanip>	// require setw
#include <sstream>	// require stringstream 
#include <cstring>	// require memset
#include <cctype>		// require tolower, toupper
#include <fstream>	// require freopen
#include <ctime>		// require srand
#define rep(i,n) for(int i=0;i<(n);i++)
#define ALL(A) A.begin(), A.end()

using namespace std;

typedef long long ll;
typedef pair<int, int> P;


int main()
{
	ios_base::sync_with_stdio(0);

	set<ll> Wsum, Hsum; Wsum.clear(), Hsum.clear();
	ll W, H; cin >> W >> H;
	int N; cin >> N;
	rep (i, N ){
		int S, K; cin >> S >> K;
		Wsum.insert (S );
		Hsum.insert (K );
	} // end rep

	ll res = W*(ll)Hsum.size() + H*(ll)Wsum.size() - (ll)Wsum.size()*Hsum.size() - N;

	cout << res << endl;

	return 0;
}