import java.util.ArrayList;
import java.util.Arrays;
import java.util.Map;
import java.util.Scanner;
import java.util.TreeMap;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int W = scan.nextInt();
		int H = scan.nextInt();
		int N = scan.nextInt();

		long ans = 0;
		int []a = new int[H + 1];
		Arrays.fill(a, 0);
		// 隣接リスト
		Map<Integer, ArrayList<Integer>> map =
				new TreeMap<Integer, ArrayList<Integer>>();
		for(int i = 0; i < N; i++) {
			int S = scan.nextInt();
			int K = scan.nextInt();
			a[K] = 1;
			if(!map.containsKey(S)) {
				ArrayList<Integer> list = new ArrayList<Integer>();
				list.add(K);
				map.put(S, list);
			}else {
				map.get(S).add(K);
			}
		}
		scan.close();
		int cnt = 0;
		for(int i = 1 ; i <= H; i++) {
			if(a[i] == 1) {
				cnt ++;
			}
		}
		for(int i = 1; i <= W; i++) {
			if(map.containsKey(i)) {
				ans += (long) (H - map.get(i).size());
			}else {
				ans += (long) cnt;
			}
		}
		System.out.println(ans);
	}
}