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

import java.util.Scanner;

/**
 *
 * @author cteam48
 */
public class ith {

    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String input = new String();
        int X;
        int Y;
        int Xk = 0;
        int Yk = 0;
        int N;
        int vystup;
        
        int moje=0;
        
        boolean Xdobre; // neohrozuje kralovna na X
        boolean Ydobre;// neohrozuje kralovna na Y
        boolean Ddob;        // TODO code application logic herere;// neohrozuje kralovna na diagonale
        boolean konec = false;
        // TODO code application logic here
        while(konec==false) {
            X  = sc.nextInt();
            Y = sc.nextInt();
            N = sc.nextInt();
            if(X==0 && Y==0 && N==0) {
                konec = true;
            } else {
                
                boolean sachovnice[][] = new boolean[X][Y];
/*               for (int i = 0; i < X; i++) {
                    for (int j = 0; j < Y; j++) {
                        sachovnice[i][j] = false;
                    }
                }
*/              
             //   System.out.println(sachovnice[0][0]);
                
                for(int i=0; i<N; i++) {
                    Xk = sc.nextInt();
                    Yk = sc.nextInt();
                    
                    //sachovnice[Xk-1][Yk-1] = true;
                    
                    //horizontal                    
                    for (int h = 0; h<X; ++h) {
                          sachovnice[h][Yk-1] = true;    
                          //moje++;
                    }
                    
                    
                    //vertical                    
                    for (int h = 0; h<Y; ++h) {
                          sachovnice[Xk-1][h] = true;   
                        //  moje++;
                    }
                    //moje--;
                   
                    Yk = Yk-1;
                    Xk = Xk-1;
                    
                    //diagonal hlavna spodok
                    for (int h =Yk;h >=0; --h) {
                        if (Xk+Yk-h >= X) {
                            break;
                        }  else {
                            sachovnice[Xk+Yk-h][h] = true;   
                            //moje++;
                        }  
                    }
                    //moje--;
                    
                    //diagonal hlavna vrch
                    for (int h =Yk;h <Y; ++h) {
                        if (Xk - (h-Yk) < 0) {
                            break;
                        }  else {
                            sachovnice[Xk - (h-Yk)][h] = true;    
                            //moje++;
                        }  
                    }
                    //moje--;
                    
                    //diagonal vedlajsia spodok
                    for (int h =Yk;h >=0; --h) {
                        if (Xk - (Yk -h) < 0) {
                            break;
                        }  else {
                            sachovnice[Xk - (Yk -h)][h] = true; 
                            //moje++;
                        }  
                    }
                    //moje--;
                    
                    //diagonal vedlajsia vrch
                    for (int h =Yk;h <Y; ++h) {
                        if (Xk + (h - Yk) >=X) {
                            break;
                        }  else {
                            sachovnice[Xk + (h - Yk)][h] = true;  
                            //moje++;
                        }  
                    }
                    //moje--;
                  
         }
                vystup = 0;
                
               for (int i = 0; i < X; i++) {
                    for (int j = 0; j < Y; j++) {
                        if (sachovnice[i][j] == false) {
                            ++vystup;
                        }
                    }
                } 
                
                System.out.println(vystup);
        }
    }

    }
}