#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <stack>
#include <queue>
#include <cmath>
#include <string>
using namespace std;
typedef long long ll;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef pair<int,int> pint;
typedef pair<ll,ll> pll;
#define range(i,a,b) for(int i=a;i<b;++i)
#define rep(i,n) range(i,0,n)
#define INF 10000000000 //10^10
#define PI 3.141592
#define pb push_back

int main(){
    ll w,h,n;
    cin >> w >> h >> n;
    vector<pll> v(n);
    rep(i,n) cin >> v[i].first >> v[i].second;
    map<int,int> mark;
    map<int,int> num;
    rep(i,n) mark[v[i].first]+=1;
    rep(i,n) num[v[i].second]+=1;
    cout << w*h-n-(w-mark.size())*(h-num.size()) << endl;
}