How do you say Using 「です」 for the negative is primarily for spoken Japanese only and is used to soften the negative aspect in conversations. On the other hand, the 「～ません」 and 「～ませんでした」 conjugations sound a bit stiff and formal and is more suitable for written Japanese. It also sounds more assertive so it would appropriate for settings such a news report, an announcement, or any formal occasion. in Japanese?