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

public class Main {
	static boolean memo[];
	static int ans, min;

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();
		long w = sc.nextLong();
		long h = sc.nextLong();
		int n = sc.nextInt();
		HashSet<Integer> hs1 = new HashSet<>();
		HashSet<Integer> hs2 = new HashSet<>();
		int mark, num;
		long sum;
		for (int i = 0; i < n; i++) {
			mark = sc.nextInt();
			num = sc.nextInt();
			hs1.add(mark);
			hs2.add(num);
		}
		sum = hs1.size() * h + (w - hs1.size()) * hs2.size() - n;
		System.out.println(sum);
	}
}