/*
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 * and open the template in the editor.
 */

import java.util.*;
import java.io.*;

/**
 *
 * @author cteam39
 */
public class ith {

    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st;
        int rows, cols, n, r, s, rx, sx, freecount;
        boolean[][] obsazeno;
        while(true) {
            st = new StringTokenizer(br.readLine());
            rows = Integer.parseInt(st.nextToken());
            cols = Integer.parseInt(st.nextToken());
            n = Integer.parseInt(st.nextToken());
            if(rows==0 && cols==0 && n==0) break;
            obsazeno = new boolean[rows][cols];
            for (int i = 0; i < n; i++) {
                st = new StringTokenizer(br.readLine());
                rx = Integer.parseInt(st.nextToken()) - 1;
                sx = Integer.parseInt(st.nextToken()) - 1;
                for (r = 0; r < rows; r++) {
                    obsazeno[r][sx] = true;
                }
                for (s = 0; s < cols; s++) {
                    obsazeno[rx][s] = true;
                }
                // doleva nahoru
                r = rx - 1;
                s = sx - 1;
                while(r > -1 && s > -1){
                    obsazeno[r][s] = true;
                    r--;
                    s--;
                }
                // doprava nahoru
                r = rx - 1;
                s = sx + 1;
                while(r > -1 && s < cols){
                    obsazeno[r][s] = true;
                    r--;
                    s++;
                }
                // doleva dolu
                r = rx + 1;
                s = sx - 1;                
                while(r < rows && s > -1){
                    obsazeno[r][s] = true;
                    r++;
                    s--;
                }
                // doprava dolu
                r = rx + 1;
                s = sx + 1;
                while(r < rows && s < cols){
                    obsazeno[r][s] = true;
                    r++;
                    s++;
                }
            }
            freecount = 0;
            for (r = 0; r < rows; r++) {
                for (s = 0; s < cols; s++) {
                    if(obsazeno[r][s] == false) {
                        freecount += 1;
                        //System.out.print("0");
                    }
                    /*else{
                        System.out.print("+");
                    }*/
                }
                //System.out.println("");
            }
            System.out.println(freecount);
        }
    }

}