#include <stdio.h>

#define MAX 20001

int main (void)
{
	int i,j,vysledek;
	int x,y,n;
	int dx,dy;
	char radky[MAX];	
	char sloupce[MAX];	
	char leva[2*MAX];	
	char prava[2*MAX];
	

	
	while (1) {
		scanf("%d %d %d", &x, &y, &n);		
		if ( x == y && y == n && n == 0) break;
		
		/* nulovani */
		vysledek = 0;

		for (i = 0; i < MAX; i++) {
			radky[i] = '0';
			sloupce[i] = '0';
		}	

		for (i = 0; i < 2*MAX; i++) {
			leva[i] = '0';
			prava[i] = '0';
		}
		/* konec nulovani */

		for (i = 0; i < n; i++) {
			scanf("%d %d",&dx,&dy);
			sloupce[dx] = '1';
			radky[dy] = '1';	

			leva[dx-dy + MAX-1] = '1';
			prava[dx+dy ] = '1';
		}
		for (i=1;i <= y;i++) {
			if (radky[i] == '1') continue; 
			for (j = 1;j <= x;j++) {
				if (sloupce[j] == '1') continue;
				if (leva[j-i + MAX - 1] == '1') continue;	
				if (prava[i+j] == '1') continue;	
				vysledek++;
			}
		}
		/*
		for (i=1;i <= y;i++) {
			for (j = 1;j <= x;j++) {
				if (radky[i] == '1' || sloupce[j] == '1' || leva[j-i + MAX -1] == '1' ||prava[i+j] == '1') 
					printf("1 ");
				else printf("0 ");
			}
			printf("\n");
		}
		*/
		/* ------------------ */
		printf("%d\n",vysledek);
	}
	return (0);	
}