Suppose you are visiting an island with knights who always tell the truth, knaves who always lie, and jokers who can do either.

You meet three islanders named Ellis, Farin and Gobi. They make the following statements:

Ellis says, "Farin is a joker."

Farin says, "Gobi is a joker."

Gobi says, "Ellis is a joker."

If you know exactly one of them is a joker, how many of them are knights?