chair to be book by means of handshakes counter ?

In a business meeting, a total of 45 handshakes occurred. How many chairs are required for all the participants to sit down?

Note:
Two people shaking hands = 1 handshake
No one shakes hands with themselves
Everyone shakes hands with everyone else
No one shakes hands with the same person more than once
No one enters or leaves the room after shaking hands and before you answer the question.