import java.util.Scanner;
public class Yuki11{
	public static void main(String[] arg){
		Scanner sc = new Scanner(System.in);
		long tempw=0,temph=0,res;
		int w,h,n,temps,tempk;
		w = sc.nextInt();
		h = sc.nextInt();
		n = sc.nextInt();
		int[] cs = new int[w];
		int[] ck = new int[h];
		for(int i = 0;i<n;i++){
			temps = sc.nextInt()-1;
			tempk = sc.nextInt()-1;
			if(cs[temps] == 0){
				cs[temps] = 1;
				tempw++;
			}
			if(ck[tempk] == 0){
				ck[tempk] = 1;
				temph++;
			}
		}
		res = (long)h*(long)tempw+(long)w*(long)temph-(long)tempw*(long)temph-(long)n;
		System.out.println(res);
	}
}