#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <sstream>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <numeric>
#include <cctype>
#include <tuple>
#include <climits>
#include <bitset>
#include <cassert>
#include <random>

#ifdef _MSC_VER
#include <agents.h>
#endif

#define FOR(i, a, b) for(int i = (a); i < (int)(b); ++i)
#define rep(i, n) FOR(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define REV(v) v.rbegin(), v.rend()
#define MEMSET(v, s) memset(v, s, sizeof(v))
#define UNIQUE(v) (v).erase(unique(ALL(v)), (v).end())
#define MP make_pair
#define MT make_tuple

using namespace std;

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

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);

	ll w, h, n;
	cin >> w >> h >> n;

	set<int> W, H;
	rep(i, n){
		int s, k;
		cin >> s >> k;
		W.insert(s);
		H.insert(k);
	}

	ll ans = h*W.size() + w*H.size() - W.size()*H.size() - n;
	cout << ans << endl;

	return 0;
}