HELP SOMEONE

#include <stdio.h>

  int main(void)  
{
    double sell, earn;
    int stop;
    stop = 0;
    
    while ( stop != -1 )
  {
    printf ("Enter sales in dollars (-1 to end): ");
    scanf ("%lf",&sell);
    if ( sell == -1 )
    {
        stop = -1;
    }
    else
    {
    earn = ( sell / 100 * 9 ) + 200;
    printf ("Salary is: $%f\n\n",earn);
    }
  }
    
    
  system ("PAUSE");
  return (0);
    


    
}