public static ListNode getMiddle(ListNode head){
		
		if(head==null||head.next==null){
			return head;
		}
		
		ListNode slow = head;
		ListNode fast = head.next;
		
		while(fast.next!=null&&fast!=null){
			slow = slow.next;
			fast = fast.next.next;
		}
		
		return slow;
		
	}