import java.util.Scanner;

class Yuki11{
	public static final int  MAX_DATA = 1000000;
	public static boolean[] mark = new boolean[MAX_DATA+1];
	public static boolean[] number = new boolean[MAX_DATA+1];

	public static void main(String[] args){
		Scanner stdIn = new Scanner(System.in);
		int w = stdIn.nextInt();
		int h = stdIn.nextInt();
		int n = stdIn.nextInt();
		int countStype = 0;
		int countKtype = 0;

		for(int i=0;i<n;i++){
			int s = stdIn.nextInt();
			int k = stdIn.nextInt();
			if(mark[s]==false){
				countStype++;
				mark[s]=true;
			}
			if(number[k]==false){
				countKtype++;
				number[k]=true;
			}
		}
		//System.out.println(w+" "+h+" "+n+" "+countStype+" "+countKtype);
		int answer = (h*countStype) + (w*countKtype) - (countStype*countKtype) - n;
		System.out.println(answer);


	}
}