import java.util.*;

public class ith{

	
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		while(true){
			int a = sc.nextInt();
			int b = sc.nextInt();
			int c = sc.nextInt();
			
			if (a==0 && b==0 && c==0)
				break;
			
			boolean[][] pole = new boolean[a+1][b+1];
								
			sc.nextLine();
					
			for (int i = 0; i< c;i++){
				int x = sc.nextInt();
				int y = sc.nextInt();
				sc.nextLine();
	
				int m,n;
				m = x-1;
				n = y-1;
				while(m>0 && n>0)
				{
					pole[m][n]=true;
					m--;
					n--;
				}
				
				m = x+1;
				n = y+1;
				while(m<=a && n<=b)
				{
					pole[m][n]=true;
					m++;
					n++;
				}
				
		
				m = x+1;
				n = y-1;
				while(m<=a && n>0)
				{
					pole[m][n]=true;
					m++;
					n--;
			
				}
				
				m = x-1;
				n = y+1;
				while(m>0 && n<=b)
				{
					pole[m][n]=true;
					m--;
					n++;
				}
				
								
				m = x-1;
				while(m>0)
				{
					pole[m][y]=true;
					m--;
				}
				
				m = x+1;
				while(m<=a)
				{
					pole[m][y]=true;
					m++;
				}
				
				n = y-1;
				while(n>0)
				{
					pole[x][n]=true;
					n--;
				}
				
				n = y+1;
				while(n<=b)
				{
					pole[x][n]=true;
					n++;
				}
								
				
			}
			
			int v = a*b;		
			for(int i = 1;i<=a;i++)
				for(int o = 1;o<=b;o++)
					if(pole[i][o]==true)
						v--;	
			
			System.out.println(""+v);
		
		}
	
	}
}