#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <iostream>
#include <queue>
#include <list>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;


int main(){
  ll W, H, N, s, k;
  set<ll> S, K;

  cin >> W;
  cin >> H;
  cin >> N;
  rep(i,N){
    cin >> s >> k;
    S.insert(s);
    K.insert(k);
  }

  ll snum = S.size(), knum = K.size();

  ll ret = (snum*H) + (knum*W) - 2 * (snum * knum) + (snum * knum - N);
  cout << ret << endl;
  
  
  return 0;
}