void gcd(short unsigned int a, short unsigned int b, short unsigned int *outp)
{
  short unsigned int result = 0;
  short unsigned int x, y;
  
  x = a;
  y = b;
  
  if ((x!=0) && (y!=0))
  {
    while (x != y)
    {
      if (x >= y)
      {
        x = x - y;
      }
      else
      {
        y = y - x;
      }
    }
    result = x;
  }
  else
  {
    result = 0;
  }
  
  *outp = result;      
}