Solve this probability question:

an airplane has 50 seats, and each of its 50 passengers shows up with his/her ticket that has assigned seat. the first person to enter the plane forgets to look at his ticker and chooses a seat on random. each next person to enter the plane takes his assigned seat(if available or chooses a seat on random(if his/her seat his taken). what is the probability that the last passenger gets to sit in his assigned seat?