#include <stdio.h>

int gdiad(int r, int s) 
{
    return s+(20000-r);
}

int gdiau(int r, int s)
{
    return r+s;
}

int main(void)
{
    char riadky[20000];
    char stlpce[20000];
    char diad[40000];
    char diau[40000];
    int r, s;
    int sx, sy, nq;
    int i, j, vol;
    
    while (1) {
	scanf("%d %d %d\n", &sx, &sy, &nq);
	if (sx==0 && sy==0 && nq==0)
	    break;
	for (i=0; i<20000; i++) {
	    riadky[i]=0;
	    stlpce[i]=0;
	    diad[i]=0;
	    diau[i]=0;
	}
	for (i=20000; i<40000; i++) {
	    diad[i]=0;
	    diau[i]=0;
	}
	for (i=0; i<nq; i++) {
	    scanf("%d %d\n", &s, &r);
	    s--;
	    r--;
	    riadky[r]=1;
	    stlpce[s]=1;
	    diad[gdiad(r,s)]=1;
	    diau[gdiau(r,s)]=1;
	}
	vol = 0;
	for (r=0; r<sy; r++) {
	    if (riadky[r])
		continue;
	    for (s=0; s<sx; s++) {
		if (stlpce[s]==0 && diad[gdiad(r,s)]==0 && diau[gdiau(r,s)]==0)
		    vol++;
	    }
	}
	printf("%d\n", vol);
    }
	
    return 0;
}