#include <iostream>

using namespace std;
const int DAMA = 2;
const int OBSAZENO = 1;
const int PRAZDNO = 0;





int main()
{
 
int velx,vely,N,qx,qy;
while (1)
{
scanf("%d %d %d",&velx,&vely,&N); // NACITANI VELIKOSTI A POCTU DAM
if ((velx == 0) and (vely==0) and (N==0)) return 0;
int sachovnice[velx+1][vely+1];
for (int dx = 0;dx<=velx;dx++) for (int dy = 0;dy<=velx;dy++) sachovnice[dx][dy] = 0; //vynulovani
for (int q=1;q<=N;q++)
{
scanf("%d %d",&qx,&qy);

sachovnice[qx][qy]=DAMA;

sachovnice[qx][0]= OBSAZENO;
sachovnice[0][qy]= OBSAZENO;
///------------
int sqx = qx;
int sqy = qy;
// hlavni diagonala
while ((sqx != 1) and (sqy !=1))
{
sqx-=1;
sqy-=1;
}
for (sqx,sqy;(sqx<=velx and sqy<=vely);sqx++,sqy++)
	{
	//cout << sqx <<" " <<sqy << endl;
	sachovnice[sqx][sqy] = OBSAZENO;	
	}
// vedlejsi
sqx = qx;
sqy = qy;
while ((sqy !=vely) and (sqx != 1))
{
sqx-=1;
sqy+=1;
//cout << sqx <<" " <<sqy << endl;
}
for (sqx,sqy;(sqx<=velx and sqy>=1);sqx++,sqy--)
	{
	//cout << sqx <<" " <<sqy << endl;
	sachovnice[sqx][sqy] = OBSAZENO;	
	}
} // konec kralovny
int soucet = 0;
for (int dx=1;dx<= velx;dx++)
 {
	if (sachovnice[dx][0]!=OBSAZENO) 
 	for (int dy=1;dy<= vely;dy++)
  	{
  	if (sachovnice[0][dy]!=OBSAZENO) 
		if (sachovnice[dx][dy]==PRAZDNO) soucet++;
  	} 
 }


cout << soucet <<endl;




}
}