private ListNode mergeListNode(ListNode ln1, ListNode ln2)
    {
    	if(ln1 == null) return ln2;
    	if(ln2==null) return ln1;
    	ListNode tail= null;
    	ListNode head=null;
    	ListNode cur=null;
    	while (ln1!=null && ln2!=null)
    	{
    		
    		if(ln1.val<=ln2.val )
    		{
    			cur = ln1;
    			ln1=  ln1.next;
        	}
        	else if(ln1.val>ln2.val )
        	{
        		cur = ln2;
        		ln2 = ln2.next;
        	}
    		if (head==null)
			{
				head= cur;
				tail = cur;
			}
			else
			{
				tail.next = cur;
				tail= tail.next;
			}
    	}
    	if (ln1==null) tail.next = ln2;
    	if (ln2==null) tail.next = ln1; 
    	return head;
    	
    }