//package ith;

import java.util.Scanner;

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


        public static void main(String[] args) {
           Scanner sc = new Scanner(System.in);
           boolean konec = false;
            int X;
            int Y;
            int N;  

            while(konec==false) {
                X  = sc.nextInt();
                Y = sc.nextInt();
                N = sc.nextInt();
                if(X==0 && Y==0 && N==0) {
                    konec = true;
                } else {
                    int vysledek = 0;
                    boolean sloupec[] = new boolean[X];
                    boolean radek[] = new boolean[Y];
                    int vetsi;
                    int mensi;
                    if(X>Y) {
                        vetsi=X;
                        mensi=Y;
                    } else {
                        vetsi=Y;
                        mensi=X;
                    }
                    boolean rozdil1[] = new boolean[2*vetsi];
                    boolean rozdil2[] = new boolean[2*vetsi];
                    
                    for(int i=0; i<N; i++) {
                        int Xk = sc.nextInt();
                        int Yk = sc.nextInt();
                        sloupec[Xk-1] = true;
                        radek[Yk-1] = true;

                            rozdil1[Xk-Yk+vetsi]=true;
                            rozdil2[(X-Xk+1)-Yk+vetsi]=true;
                           // System.out.println((Xk-Yk-(X-Y)+vetsi)+"/"+((X-Xk-1)-Yk-(X-Y)+vetsi));

                    }
                    
                    for (int i = 0; i < X; i++) {
                        if(sloupec[i]==false) {
                            for (int j = 0; j < Y; j++) {
                                if(radek[j]==false) {
                                    //System.out.println( (vetsi+i-j) + "/" + (2*vetsi-i-j));

                                        if(rozdil1[i-j+vetsi]==false && rozdil2[(X-i-1)-j+vetsi]==false) vysledek++;
                                    
                                    //System.out.println(vetsi+i-j);
                                }

                            }
                        }
                    }

                    System.out.println(vysledek);
                    
                    
                }
            }
            
        }
}