public class IntListDriver
{
	public static void main(String[] args)
	{
		IntNode head=null;
		for (int i = args.length - 1 ; i >= 0 ; i--) {
			head = new IntNode(Integer.parseInt(args[i]), head);
		}
 
 
		IntList list = new IntList();
		list.head=head;
 
		double result;
		result=list.getAverage();
		System.out.println(result);
	}
}

public class IntList
{
	public IntNode head; // DO NOT MAKE THIS FIELD PRIVATE
	public IntList()
	{
		head = null;
	}
 
	public double getAverage()
	{
		double count=0;
		double average=0;
		IntNode pos=head;
		while (pos!=null)
		{
			count++;
			average=average+pos.data;
			pos=pos.next;
		}
		
		average=average/count;
		return average;
		else	
		{
			return null;
		}
		
		//ERROR CONDITIONS!
	}
 
	public void addAfterEvery(int oldvalue, int newvalue)
	{
		IntNode pos=head;
		IntNode prev=null;
		while (pos!=null)
		{
			if (oldvalue==pos.data)
			{	
				prev=pos.next;
				IntNode newNode=new IntNode();
				newNode.data=newvalue;
				pos.next=newNode;
				newNode.next=prev;
				pos=newNode.next;
			}
			else
			{
				pos=pos.next;
			}	
		}
	}
 
	public void moveToFront(int value)
	{
		IntNode pos=head;
 
		if (pos==null)
		{
			return;
		}
		
		IntNode p=null;
 
		while (pos.next!=null)
		{
			if (value==pos.next.data)
			{
				p=pos;
				pos=pos.next;
				if (pos!=null)
				{
					p.next=pos.next;
					pos.next=head;
					pos=p;
				}
			}
			else
			{
				pos=pos.next;
			}
		}
 
			
	}
 
	public void reverse()
	{
		//IntNode
		//pos.next=null;
		//while (pos.next!=null)
		//{
		//	pos.next=pos;
		//	
		//}
		//head=pos;
		
	}
	
	public int countCommonValues(IntList other)
	{
		IntNode pos=head;
		IntNode posother=other.head;
		
		int count=0;
		while (pos!=null)
		{
			if (pos==posother)
			{
			count++;
			pos=pos.next;
			posother=posother.next;
			}
			else
			{
			pos=pos.next;
			posother=posother.next;
			}
		}
		return count;
	}
}