#include <set>
#include <map>
#include <list>
#include <queue>
#include <stack>
#include <cmath>
#include <ctype.h>
#include <ctime>
#include <cstdio>
#include <vector>
#include <string>
#include <bitset>
#include <cctype>
#include <cstdlib>
#include <cstring>
#include <utility>
#include <numeric>
#include <complex>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <cassert>
#include <iostream>
#include <iterator>
#include <algorithm>
#define aLL(g) (g).begin(),(g).end()
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define F(i,j,k) fill(i[0],i[0]+j*j,k)
#define P(p) cout<<(p)<<endl;
#define EXISt(s,e) ((s).find(e)!=(s).end())
#define INF 1<<25
#define MAX 100000000
#define pb push_back
using namespace std; 
typedef vector<int> vi;
typedef vector<long long> vl;
typedef vector<double> vd;
typedef pair<int,int> pii;
typedef pair<long,long> pll;
typedef long long ll;
int dx[] = {0,1,0,-1};
int dy[] = {-1,0,1,0};

int sttoi(std::string str){int ret;std::stringstream ss;ss << str;ss >> ret;return ret;}

int table[10001];

int main(){
 int w,h,n;
 cin >> w >> h >> n;
 int count = 0;
 bool usedflag[w+1][h+1] = {};
 for(int i = 1;i <= w;i++){
  for(int j = 1;j <= h;j++){
    usedflag[i][j] = true;
  }
 }
 vector<pair<int,int> > v;
 vector<pair<int,int> >::iterator it;
 for(int i = 0;i < n;i++){
  int a,b;
  cin >> a >> b;
  v.push_back(make_pair(a,b));
 }
 for(it = v.begin();it != v.end();it++){
  for(int i = 1;i <= w;i++){
    if(i != (*it).first && usedflag[i][(*it).second]){
      usedflag[i][(*it).second] = false;
      count++;
    }
  }
  for(int i = 1;i <= h;i++){
    if(i != (*it).second && usedflag[(*it).first][i]){
      usedflag[(*it).first][i] = false;
      count++;
    }
  }
 }
 P(count);
}