import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Queue;

public class No11 {

	public static void main(String[] args) throws IOException{
		//カードマッチ
		String[] text = readStr();
		int W = Integer.parseInt(text[0]);
		int H = Integer.parseInt(text[1]);
		int N = Integer.parseInt(text[2]);
		int S , K , count = 0;
		Queue<Integer> qu = new ArrayDeque<>();
		
		int[][] hand = new int[W + 1][H + 1];
		for(int i = 0;i < N;i++) {
			S = Integer.parseInt(text[i + 3].split(" ")[0]);
			K = Integer.parseInt(text[i + 3].split(" ")[1]);
			
			hand[S][K] = 1;
			qu.add(S);
			qu.add(K);
		}
		
		for(int i = 0;i < N;i++) {
			S = qu.poll();
			K = qu.poll();
			
			for(int kn = 1;kn <= H;kn++) {
				if(hand[S][kn] != 1) {
					count++;
					hand[S][kn] = 1;
				}
			}
			for(int sn = 1;sn <= W;sn++) {
				if(hand[sn][K] != 1) {
					count++;
					hand[sn][K] = 1;
				}
			}
		}
		
		System.out.println(count);

	}
	
	public static String[] readStr() throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		ArrayList<String> list = new ArrayList<>();

		do {
			list.add(br.readLine());
		}while(br.ready());

		br.close();

		String[] text = new String[list.size()];
		list.toArray(text);

		return text;

	}

}