import java.util.Scanner;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author cteam46
 */
public class ith {
    
    
    static boolean[][] pole;
    static int x,y,n;
    
    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        
        while(true) {
            
        x = sc.nextInt();
        y = sc.nextInt();
        n = sc.nextInt();
        sc.nextLine();
        
     
        //vzpneme        
        if(x == 0 && y == 0 && n == 0 ) return;
        pole = new boolean[x+4][y+4];
            for (int i = 0; i < n; i++) {
                int kx,ky ;
             //   System.out.println("yadej kralovnu");
                kx = sc.nextInt() ;
                ky = sc.nextInt();
                sc.nextLine();
                
                kx --;
                ky --;
                nastavPole(kx, ky);
            }
        
//      vypis();
      
               System.out.println(pocetPoli());     
        
        
        }
        
        
    
    
    }
    

    public static void vypis() {
       //     System.out.println("--------------------------------------------------------------------");        
        for (int i = 0; i < y; i++) {
            for (int j = 0; j < x; j++) {
            System.out.print(" "+(pole[j][i] ? "1" : "0"));                
            }
            System.out.print("\n");
        //    System.out.println("--------------------------------------------------------------------");

        }

        
    }
    
    
    public static int pocetPoli() {
        int res = 0;
        
        for (int i = 0; i < x; i++) {
            for (int j = 0; j < y; j++) {
              if(pole[i][j] == false) res ++;
            }
        }

        
        return res;
    }
     
    public static void nastavPole(int kx, int ky) {
               
        for (int i = 0; i < y; i++) {
            pole[kx][i] = true;            
        }
        
        for (int j = 0; j < x; j++) {
            pole[j][ky] = true;
        }           
        
        int dy,dx;             
        
        dy = ky - Math.min(kx, ky);            
        dx = kx - Math.min(kx, ky);
        
        while(dx < x && dy < y) {          
            if(dx >= 0 && dx < x && dy >= 0 && dy <y) {
                pole[dx][dy] = true;
            }
            dx++;
            dy++;            
        }
         
        dy = ky + Math.min(kx, y-1 - ky);
        dx = kx - Math.min(kx, y-1 - ky);
        
         while(dx < x && dy >= 0) {            
            if(dx >= 0 && dx < x && dy >= 0 && dy <y) {
                pole[dx][dy] = true;
            }
            dx++;
            dy--;            
        }
        
           
                
    }
    

}