#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>

#define p(s) cout<<(s)<<endl
#define REP(i,n,N) for(int i=n;i<N;i++)
#define RREP(i,n,N) for(int i=N-1;i>=n;i--)
#define CK(n,a,b) ((a)<=(n)&&(n)<(b))
#define F first
#define S second
typedef long long ll;
using namespace std;
const int inf=1e9+7;

ll W,H,N;
ll s, k;
set<ll> mc, mn;
int main(){
    cin>>W>>H>>N;
    REP(i,0,N){
        cin>>s>>k;
        mc.insert(s);
        mn.insert(k);
    }
    ll ans = W*H - (W-mc.size()) * (H-mn.size()) - N;

    p(ans);

    return 0;
}