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

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

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

    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    static StringTokenizer st;
    static int rows,  cols,  n,  d,  r,  s,  rx,  sx,  freecount;
    static boolean[] xr,  xs, drd, dld;
    static boolean free;
    //static boolean[][] obsazeno;
    public static void main(String[] args) throws Exception {

        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;
            }
            xr = new boolean[rows+1];
            xs = new boolean[cols+1];
            drd = new boolean[rows+cols];
            dld = new boolean[rows+cols];
            //obsazeno = new boolean[rows][cols];
            for (int i = 0; i < n; i++) {
                st = new StringTokenizer(br.readLine());
                r = Integer.parseInt(st.nextToken());
                s = Integer.parseInt(st.nextToken());
                xr[r] = true;
                xs[s] = true;
                drd[s-r+rows] = true;
                dld[cols-s-r+1+rows]=true;
            }
            freecount = 0;
            for (r = 1; r < rows+1; r++) {
                if(xr[r]) continue;
                for (s = 1; s < cols+1; s++) {
                    if(xs[s]) continue;
                    if(!drd[s-r+rows] && !dld[cols-s-r+1+rows]) freecount++;
                }
            }
            System.out.println(freecount);
        }
    }
}