public class sep23
{

public static void main(String[] args)
{ intList A, B, C;
  A = new intList();
  A.front = new cell(1,new cell(3,new cell(5,new cell(7,null))));
//  A.print();
  A.insertAt(6,2);  // insert 6 at position 2
  A.insertAt(3,3);  // insert 3 at position 3
  A.print();
  
  A.delete(3);
  A.print();
  A.delete(1);
  A.print();

} // end main

} // end class sep23


class cell    	// "cons" cell
{  int head;    // datum
   cell tail;   // pointer to rest of the list
   public cell(int h, cell t)  { head = h; tail = t; }
} // end class cell


class intList 
{
  cell front;  	// points to a list
  
  public void print()
  { cell i;     // pointer to go through the list
    for(i=front;i != null;i=i.tail) 
       System.out.print(i.head + " ");
    System.out.println("");
  }

  public void insert_front(int newint)
   { front = new cell(newint,front); }

  public void insertAt(int newint, int pos)
  { // assume 0 is front of the list 
    cell current = front;
    int counter = 0;
    if (pos == 0) front = new cell(newint,front);
      else
       {
        while ( (current != null) && (counter < (pos -1)) )
         {  counter = counter + 1;
            current = current.tail;
         }
        if (current != null)
          { cell newcell =  new cell(newint,current.tail);
            current.tail = newcell;
          }
       }  // end else

  } // end insertAt
  
  // delete first cell containing x at head
  public void delete(int x) 
   {  cell current = front;
      if (front != null)
       { 
         if (front.head == x) front = front.tail;
           else
            {
	      while ( (current.tail != null)  &&
	              (current.tail.head != x) )
                 { current = current.tail; }
              if (current.tail != null)
                 current.tail = current.tail.tail; 
	    } // end else
       } // end outer if
   }


} // end wrapper class intList