int main(void)
{
  int x = 3;
  int y = 11;
  int *p = &x;
  int *q = &y;
  int tmp;

  printf("%d %d\n",x,y);
  tmp = *p;
  *p = *q;
  *q = tmp;
  printf("%d %d\n",x,y);
  return 0;
}