/* Test of recursion-handling. */
class recur {
  int next;
  recur tail;

  /* no side-effect */
  static int length(recur r) {
    if (r == null)
      return 0;
    else
      return 1 + length(r.tail);
  }

  /* Modifies both args. */
  static void mod1(recur left, recur right) {
    mod2(right, left);
  }

  /* Modifies both args. */  
  static void mod2(recur left, recur right) {
    mod1(left, right); // change to mod1(right, left); for more fun
    right.next = 5;
  }

  public static void  main(String[] args) {
    mod1(null, null);
    int z = length(null);
  }
}