PROGRAM IS

VAR N := 9;
TYPE btree IS RECORD k: INTEGER; l: btree; r: btree; END;

PROCEDURE insert (t: btree; i: INTEGER) : btree IS
  BEGIN
    IF (t = NIL) THEN
      RETURN btree {k := i; l := NIL; r := NIL};
    ELSIF (t.k <= i) THEN
      RETURN btree {k := t.k; l := t.l; r := insert(t.r,i) };
    ELSE 
      RETURN btree {k := t.k; l := insert(t.l,i); r := t.r };
    END;
  END;

PROCEDURE readtree () : btree IS
  VAR i := 0;
  VAR t : btree := NIL;
  VAR a := 0;
  BEGIN
    WHILE i < N DO
       READ (a);
       t := insert(t,a);
       i := i + 1;
    END;
    RETURN t;
  END;

PROCEDURE writetree (t : btree) IS
  BEGIN
    IF t = NIL THEN
      RETURN;
    ELSE 
      writetree(t.l);
      WRITE(t.k);
      writetree(t.r);
    END;
  END;

VAR t : btree := NIL;
BEGIN
  t := readtree();
  writetree (t);
END;