import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long W = sc.nextLong();
        long H = sc.nextLong();
        long N = sc.nextLong();
        Set<String> SSet = new HashSet<>();
        Set<String> KSet = new HashSet<>();
        for(int i=0; i<N; i++){
            String S = sc.next();
            SSet.add(S);
            String K = sc.next();
            KSet.add(K);
        }
        long a = SSet.size();
        long b = KSet.size();
        long ans = W*H-(W-a)*(H-b)-N;
        System.out.println(ans);
    }
}