#include<bits/stdc++.h>
#define ll long long 
#define mp make_pair 
#define f(i,n) for(int i=0;i<n;i++) 
#define F first 
#define S second 
#define pb push_back 
#include <ext/pb_ds/assoc_container.hpp> 
#include <ext/pb_ds/tree_policy.hpp> 
using namespace __gnu_pbds; 
  
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> 


using namespace std;

void test(){
	ll h,w,m;
	cin>>h>>w>>m;
	vector<pair<ll,ll> > row,col;
	f(i,m){
		ll a,b;
		cin>>a>>b;
		a--,b--;
		row.pb({a,b});
		col.pb({b,a});
	}
	if(m==0){
		cout<<h*w<<"\n";
		return ;
	}
	
	sort(row.begin(),row.end());
	
	ll r_res[h], c_res[w];
	f(i,h)r_res[i]=w+1;
	f(i,w)c_res[i]=h+1;
	f(i,m){
		r_res[row[i].F] = min(r_res[row[i].F],row[i].S+1);
		c_res[col[i].F] = min(c_res[col[i].F],col[i].S+1);
	}
	
	ll res = 0;
	f(i,c_res[0]-1){
		res = res + r_res[i]-1;
	}
	f(i,r_res[0]-1){
		res = res + c_res[i]-1;
	}
	
	// remove repeated cases 
	
	ordered_set st;
	
	int in = 0;
		
	f(i,c_res[0]-1){
		while(in<m and row[in].F==i){
			st.insert((int)row[in].S);
			in++;
		}
		
		// out of these columns find no's which are less than to r_res[i]-1, r_res[0]-1
		
		ll rem = st.order_of_key(min(r_res[i]-1,r_res[0]-1));
		
		res = res - (min(r_res[i]-1,r_res[0]-1)-rem);		
	}
	cout<<res<<"\n";
}

int main(){
	std::ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int tests=1;
//	 cin>>tests;
	while(tests--){
		test();
	}
}