private static ListNode buildList(int[] arr) {
		ListNode head = new ListNode(0);
		ListNode curr = head;
		for (int i : arr) {
			curr.next = new ListNode(i);
			curr = curr.next;
		}
		curr = head;
		while (curr.next != null) {
			curr = curr.next;
			if (curr.next == null) {
				curr.next = head.next.next.next.next;
				break;
			}
		}
		return head.next;
	}