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

public class Main {
    public static void main(String[] args) {
        try (Scanner scan = new Scanner(System.in)) {
            int W = scan.nextInt();
            int H = scan.nextInt();
            int N = scan.nextInt();
            HashSet<Integer> wList = new HashSet<>();
            HashSet<Integer> hList = new HashSet<>();
            for(int i=0; i<N; i++) {
                wList.add(scan.nextInt());
                hList.add(scan.nextInt());
            }
            int w = wList.size();
            int h = hList.size();
            int ans = w*H + h*W - w*h - N;
            System.out.println(ans);
        }
    }
}