import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;


public class Main_yukicoder11 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int w = sc.nextInt();
        int h = sc.nextInt();
        int n = sc.nextInt();

        Set<Integer> hsw = new HashSet<Integer>();
        Set<Integer> hsh = new HashSet<Integer>();

        for (int i = 0; i < n; i++) {
        	int s = sc.nextInt();
        	int k = sc.nextInt();
        	hsw.add(s);
        	hsh.add(k);
        }

        System.out.println((long)hsw.size() * h + hsh.size() * w - (long)hsw.size() * hsh.size() - n);
        
        sc.close();
    }
}