import java.io.*;

class UseLists1
{
 public static void main(String[] args)
 throws IOException
 {
  BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
  String str;
  List l1, l2, l3;
  System.out.println("Enter list 1: ");
  str = in.readLine();
  l1 = List.fromString(str);
  System.out.println("Enter list 2: ");
  str = in.readLine();
  l2 = List.fromString(str);
  l3 = append(l1,l2);
  System.out.println("Appending the first to the second gives: ");
  System.out.println(l3);
  l3 = revAppend(l1,l2);
  System.out.println("Reversed appending the first to the second gives: ");
  System.out.println(l3);
  System.out.println("The lists are still: ");
  System.out.println(l1);
  System.out.println(l2);
 }

 public static List append(List l1,List l2)
 {
  if(l1.isEmpty())
     return l2;
  else
     return append(l1.tail(),l2).cons(l1.head());
 }

 public static List revAppend(List l1,List l2)
 {
  while(!l1.isEmpty())
     {
      l2=l2.cons(l1.head());
      l1=l1.tail();
     }
  return l2;
 }
}