public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
		
		ListNode head = new ListNode(0);
		ListNode list = head;
		
		while(l1 != null && l2 != null) {
			if (l1.val <= l2.val) {
				list.next = l1;
				list = list.next;
				l1 = l1.next;				
			}
			else {
				list.next = l2;
				list = list.next;
				l2 = l2.next;
			}
		}
		
		if (l1 != null) list.next = l1;
		if (l2 != null) list.next = l2;
		
		return head.next;		
        
    }