import java.util.*;

public class Main {
   public static void main(String[] args) throws Exception {
       Scanner koko = new Scanner(System.in);
       long w = koko.nextLong();
       long h = koko.nextLong();
       int n = koko.nextInt();
       int[] s = new int[n];
       int[] k = new int[n];
       for(int i=0; i<n; i++){
           s[i]=koko.nextInt();
           k[i]=koko.nextInt();
       }
       Arrays.sort(s);
       Arrays.sort(k);
       long counts=1;
       long countk=1;
       for(int i=1; i<n; i++){
           if(s[i]!=s[i-1]){
               counts++;
           }if(k[i]!=k[i-1]){
               countk++;
           }
       }
       long a = countk*w;
       long b = h-countk;
       long ans=(a-n)+(counts*b);
       System.out.println(ans);
   }
}