DoubleLink rev_double(DoubleLink L,int n)
{
	if(L==NULL||L->next==NULL)
		return L;
	DoubleLink p=L;
	L=L->next;
	p->next=NULL;

	DoubleLink t;
	printf("%d",n);
	for(int i=0;i<n-1;i++)
	{
		t=L;
		L=L->next;
		t->next=p;
		p->prev=t;
		t->prev=NULL;
		p=t;
	}
	return p;
}