でたらめじゃないです
出鱈目じゃないです
detaramejanaidesu

Noun
Desu Copula
na-Adjective
Negation Auxiliary

The polite negative form of でたらめ

1. It's not nonsense.; It's not made up.; It's not arbitrary.

Negative
Polite
Casual Register
Usually Written in Kana