import java.io.*;

public class ith {
	public static void main(String[] args) throws Exception {
		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String l;
		short[] ign_x, ign_y;
		int xc, yc;
		short[][] queens;
		
		
		String[] p;
		short w, h, n;
		short x,y;
		int free;
		
		while(true) {
			l = br.readLine();
			if(l.equals("0 0 0")) break;
			
			p=l.split(" ");
			w = (short)Integer.parseInt(p[0]);
			h = (short)Integer.parseInt(p[1]);
			n = (short)Integer.parseInt(p[2]);
			xc = 0;
			yc = 0;
			ign_x = new short[w];
			ign_y = new short[h];
			
			free = 0;
			
			queens = new short[n][2];
			boolean ign;
			boolean breakx;
			boolean isfree;
			int pdif, qdif;
			for(int i = 0; i<n; i++) {
				l = br.readLine();
				p = l.split(" ");
				queens[i][0] = (short)(Integer.parseInt(p[0])-1);
				queens[i][1] = (short)(Integer.parseInt(p[1])-1);
			}
			for(x = 0; x<w; x++) {
				ign = false;
				breakx = false;
				for(int i = 0; i<xc; i++) {
					if(ign_x[i] == x) {
						ign = true;
						break;
					}
				}
				if(ign) continue;
				for(y = 0; y<h; y++) {
					ign = false;
					for(int i = 0; i<yc; i++) {
						if(ign_y[i] == y) {
							ign = true;
							break;
						}
					}
					if(ign) continue;
					isfree = true;
					for(int i = 0; i<n; i++) {
						if(x == queens[i][0]) {
							isfree = false;
							ign_x[xc++] = x;
							breakx = true;
							break;
						}
						if(y == queens[i][1]) {
							isfree = false;
							ign_y[yc++] = y;
							break;
						}
						pdif = x-queens[i][0];
						qdif = y-queens[i][1];
						if(pdif == qdif) {
							isfree = false;
							break;
						}
						if(pdif+qdif == 0) {
							isfree = false;
							break;
						}
					}
					if(isfree) {
						free++;
					}
					if(breakx) {
						break;
					}
				}
			}
			
			
			
			System.out.println(free);
		}
		
	}

}