#include<iostream>
#include<vector>
#include<cmath>
#include<climits>
#include<algorithm>
#include<queue>
#include<tuple>
#include<set>

using namespace std;  
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
#define rep(i,n) for(ll i=0;i<(n);i++)  
#define pii pair<int,int>
#define piii pair<int,pii>
#define mp make_pair
#define pb push_back  
#define ALL(a) (a).begin(),(a).end()
#define FST first
#define SEC second  
const int INF = (INT_MAX/2);
const ll LLINF = (LLONG_MAX/2);
const double eps = 1e-5;
const double PI = M_PI;
#define DEB cerr<<"!"<<endl
#define SHOW(a,b) cerr<<(a)<<" "<<(b)<<endl
#define SHOWARRAY(ar,i,j) REP(a,i)REP(b,j)cerr<<ar[a][b]<<((b==j-1)?((a==i-1)?("\n\n"):("\n")):(" "))


int main(){
  ll w,h,n; cin >> w >> h >> n;
  set<int> ss;
  set<int> sn;
  rep(i,n){
    int s,k; cin >> s >> k;
    ss.insert(s);
    sn.insert(k);
  }
  SHOW(ss.size(),sn.size());
  cout << w*h - (h-sn.size())*(w-ss.size()) - n << endl;
}