def Merge(head1, head2):	if head1 == None: return head2	if head2 == None: return head1	psuhead = ListNode(-1)	tail = psuhead	while head1 and head2:		if head1.val < head2.val: 			cur = head1			head1 = head1.next		else:			cur = head2			head2 = head2.next		cur.next = tail.next		tail.next = cur		tail = cur		Print(psuhead)	# link the rest nodes	if head1 == None: head1 = head2	tail.next = head1	head1 = psuhead.next	del psuhead	psuhead = None	return head1