#include <stdio.h>

int main()
{
    int a, b, c;
    while(1)
    {
      scanf("%d %d %d", &a, &b, &c);
      if(a == 0 && b == 0 && c == 0) break;
      
      bool mapa[a][b];
      
      for(int i = 0; i < a; i++)
        for(int j = 0; j < b; j++)
          mapa[i][j] = 1;
      
      for(int i = 0; i < c; i++)
      {
        int x, y;
        scanf("%d %d", &x, &y);
        x--;
        y--;
        
        for(int m = 0; m < a; m++){
          mapa[m][y] = 0;
        }
        for(int m = 0; m < b; m++){
          mapa[x][m] = 0;
        }
        
        
        int m = 1;
        while(!((x-m) < 0 || (y-m) < 0))
        {
          mapa[x-m][y-m] = 0;
          m++;
        }
        
        m = 1;
        while(!((x+m) >= a || (y+m) >= b))
        {
          mapa[x+m][y+m] = 0;
          m++;
        }
        
        m = 1;
        while(!((x-m) < 0 || (y+m) >= b))
        {
          mapa[x-m][y+m] = 0;
          m++;
        }
        
        m = 1;
        while(!((x+m) >= a || (y-m) < 0))
        {
          mapa[x+m][y-m] = 0;
          m++;
        }
        
      }
      
      int res = 0;
      for(int i = 0; i < a; i++)
        for(int j = 0; j < b; j++)
          res += mapa[i][j];
          
          
      printf("%d\n", res);
    }
    
    return 0;
}