#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	int W, H, N; cin >> W >> H >> N;
	map<int, int> m;
	set<int> s;
	for (int i = 0; i < N; i++) {
		int S, K; cin >> S >> K;
		m[S]++;
		s.insert(K);
	}
	ll ans = 0;
	for (int j = 1; j <= W; j++)
		if (m.count(j)) ans += H - m[j];
		else ans += s.size();
	cout << ans << endl;
}