#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int Row[50000];
int Col[50000];
int Diag1[100000];
int Diag2[100000];

int main()
{
	int w, h, n;
	while(1)
	{
		memset(Row, 0, sizeof(Row));
		memset(Col, 0, sizeof(Col));
		memset(Diag1, 0, sizeof(Diag1));
		memset(Diag2, 0, sizeof(Diag2));
		
		scanf("%d%d%d", &w, &h, &n);
		
		if(!((w) || (h) || (n)))
		{
			return 0;
		}
		
		int x, y;
		for(int i = 0; i < n; i++)
		{
			scanf("%d%d", &x, &y);
			Row[x] = 1;
			Col[y] = 1;
			Diag1[(x - y) + 30000] = 1;
			Diag2[(x + y) + 30000] = 1;
		}
		
		int count = 0;
		for(int x = 1; x <= w; x++)
		{
			if(Row[x])
			{
				continue;
			}
			
			for(int y = 1; y <= h; y++)
			{
				if(Col[y])
				{
					continue;
				}
				
				if(!((Diag1[(x - y) + 30000]) || (Diag2[(x + y) + 30000])))
				{
					count++;
				}
			}
		}
		
		printf("%d\n", count);
	}
}