Hi, I am having a hard time understanding the question.

Formally, we shall regard as Cthulhu such an undirected graph that can be represented as a set of three or more rooted trees, whose roots are connected by a simple cycle.

What does it mean to be "represented as a set of three or more rooted trees", whose roots are connected by a simple cycle? What is a "simple cycle"?

Can anyone who solved the problem give me a hint? Thank you!