type pitem = ^item;
      item = record data: integer;
                    prev: pitem
             end;
var n, k: integer;
  top, p: pitem;
procedure add(x: integer);
begin
  new(p);
  p^.data := x;
  p^.prev := top;
  top := p
end;

procedure del;
begin
  if top<>nil then
  begin p := top^.prev;
        dispose(top);
        top := p
  end;
end;

procedure wstack;
begin
  p := top;
  while p <> nil do begin write(p^.data,' ');
                          p := p^.prev;
                    end;
  writeln;
end;

begin
  top := nil;
  for k := 1 to 9 do add(k);
  wstack;
  add(0);
  wstack;
  for k:=1 to 4 do del;
  wstack;
end.