Time to flight

There are 100 seat inside the air-plane, the number is start form 1 and end with 100.
100 passagers get the number from 1 to 100, they will follow the sequent to find their seat (Mean the number one shall go in first and followed by number and so on).
If they found that their seat have been sat by other people, then they will just simplily sit on the empty seat.

One day, a mad guy get the number 1 ticket (other passager are all "normal"), he just randomly sit. In this case, what is the Probability of the 100th people (who get the number 100) to sit on the right seat(seat number 100)?