import java.io.*;

public class ith {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String l;
		boolean[][] arr;
		String[] p;
		int w, h, n;
		int x,y;
		int free;
		
		while(true) {
			l = br.readLine();
			if(l.equals("0 0 0")) break;
			
			p=l.split(" ");
			w = Integer.parseInt(p[0]);
			h = Integer.parseInt(p[1]);
			n = Integer.parseInt(p[2]);
			free = w*h;
			arr = new boolean[w][h];
			for(int i = 0; i<n; i++) {
				l = br.readLine();
				p = l.split(" ");
				x = Integer.parseInt(p[0])-1;
				y = Integer.parseInt(p[1])-1;
				for(int j = 0; j<w; j++) {
					if(arr[j][y] == false) {
						free--;
					}
					arr[j][y] = true;
				}
				for(int j = 0; j<h; j++) {
					if(arr[x][j] == false) {
						free--;
					}
					arr[x][j] = true;
				}
				for(int j = x, k = y; j<w&&k<h; j++, k++) {
					if(arr[j][k] == false) {
						free--;
					}
					arr[j][k] = true;
				}
				for(int j = x, k = y; j>=0&&k>=0; j--, k--) {
					if(arr[j][k] == false) {
						free--;
					}
					arr[j][k] = true;
				}
				for(int j = x, k = y; j<w&&k>=0; j++, k--) {
					if(arr[j][k] == false) {
						free--;
					}
					arr[j][k] = true;
				}
				for(int j = x, k = y; j>=0&&k<h; j--, k++) {
					if(arr[j][k] == false) {
						free--;
					}
					arr[j][k] = true;
				}
				
			}
			System.out.println(free);
		}
		
	}

}