import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
import java.util.StringTokenizer;



/**
 *
 * @author cteam07
 */
public class ith {
    static int pole[][];
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        
        String line, token;
        StringTokenizer st;
        int x, y, n, kx, ky;
                
        while(true) {
            int sum = 0;
            line = br.readLine();
            st = new StringTokenizer(line);
            
            try {
                token = st.nextToken();
                x = Integer.parseInt(token);
                token = st.nextToken();
                y = Integer.parseInt(token);
                token = st.nextToken();
                n = Integer.parseInt(token);
                if(x == 0 && y == 0 && n == 0) break;
                if(x < 1 || x > 20000 || y < 1 || y > 20000 || n < 0 || n > (x*y)) continue;

                pole = new int[x][y];

                for(int i = 0; i < n; i++) {
                    line = br.readLine();
                    st = new StringTokenizer(line);
                    token = st.nextToken();
                    kx = Integer.parseInt(token);
                    token = st.nextToken();
                    ky = Integer.parseInt(token);
                    if(kx < 1 || kx > x || ky < 1 || ky > y) continue;
                    
                    vyplnRadek(kx-1);
                    vyplnSloupec(ky-1);
                    vyplnLP(kx-1, ky-1);
                    vyplnPL(kx-1, ky-1);
                }
            }
            catch(Exception ex) {
                //System.out.println(ex.toString());
                continue;
            }
            
            for (int i = 0; i < pole.length; i++) {
                for (int j = 0; j < pole[i].length; j++) {
                    if(pole[i][j] == 0) sum++;
                }
            }
            
            System.out.println(sum);
        }
    }

    public static void vyplnRadek(int x) {
        for(int i = 0; i < pole.length; i++) {
            pole[x][i] = 1; 
        }
    }
    
    public static void vyplnSloupec(int y) {
         for(int i = 0; i < pole[0].length; i++) {
            pole[i][y] = 1; 
        }
    }
    
    public static void vyplnLP(int x, int y) {
        int i = x+1;
        int j = y+1;
        for(; (i < pole.length) && (j < pole[0].length); i++, j++) {
            pole[i][j] = 1; 
        }
        
        i = x-1;
        j = y-1;
        for(; (i >= 0) && (j >= 0); i--, j--) {
            pole[i][j] = 1; 
        }
    }
    
    public static void vyplnPL(int x, int y) {
        int i = x-1;
        int j = y+1;
        for(; (i >= 0) && (j < pole[0].length); i--, j++) {
            pole[i][j] = 1; 
        }
        
        i = x+1;
        j = y-1;
        for(; (i < pole.length) && (j >= 0); i++, j--) {
            pole[i][j] = 1; 
        }
    }
    
}