Provided is a method of treating or ameliorating a number of indications in an animal, including a human, comprising administering an effective amount of a compound of the formula I or IA, . To achieve this object, an image forming system according to this invention has the following arrangement. Since this gap is formed, even when a rotation driving mechanism of a medium suffers rotation nonuniformity, two neighboring recording units never overlap each other, and destruction of recording data can be prevented.