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

public class ith {

    public static void main(String args[]) throws IOException {

        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String line = in.readLine();
        StringTokenizer tokenizer = new StringTokenizer(line);
        int x = Integer.parseInt(tokenizer.nextToken());
        int y = Integer.parseInt(tokenizer.nextToken());
        int n = Integer.parseInt(tokenizer.nextToken());
        while (!((x == 0) && (y == 0) && (n == 0))) {
            boolean[][] board = new boolean[x][y];
            boolean[]	row	= new boolean[x];
            boolean[]	col	= new boolean[y];

            for (int i = 0; i < n; i++) {
            	line = in.readLine();
            	tokenizer = new StringTokenizer(line);
            	int k = Integer.parseInt(tokenizer.nextToken()) - 1;
            	int l = Integer.parseInt(tokenizer.nextToken()) - 1;
            	row[k] = true;
            	col[l] = true;
                mark(board, k, l);

            }
            
           
            
            System.out.println(count(board,row,col));
            
            
            
            line = in.readLine();
            tokenizer = new StringTokenizer(line);
            x = Integer.parseInt(tokenizer.nextToken());
            y = Integer.parseInt(tokenizer.nextToken());
            n = Integer.parseInt(tokenizer.nextToken());
        }

    }

    public static int count(boolean[][] board, boolean[] row, boolean[] col) {
        int counter = 0;
        for (int i = 0; i < board.length; i++) {
            for (int j = 0; j < board[i].length; j++) {
                if ((board[i][j] == false) && (row[i] == false) && (col[j] == false)) {
                	counter++;
                }

            }
        }

        return counter;

    }

    public static void mark(boolean[][] board, int x, int y) {
        for (int i = 0; ((x + i) < board.length && (y + i) < board[x].length); i++) {
            board[x + i][y + i] = true;
        }
        for (int i = 0; ((x - i) >= 0 && (y - i) >= 0); i++) {
            board[x - i][y - i] = true;
        }
        for (int i = 0; ((x + i) < board.length && (y - i) >= 0); i++) {
            board[x + i][y - i] = true;
        }
        for (int i = 0; ((x - i) >= 0 && (y + i) < board[x].length); i++) {
            board[x - i][y + i] = true;
        }
    }
}