In probability theory, the birthday problem asks for the probability that, in a set of n randomly chosen people, at least two will share a birthday. The birthday paradox is that, counterintuitively, the probability of a shared birthday exceeds 50% in a group of only 23 people. for more information you can read :https://brilliant.org/wiki/birthday-paradox/

and the code has 3 part firt part (A): caculate 23 people in 365 day.

second part (B): caculate k people in n day according to hat user enter.

third part (C): plot a graph of probibilety from 1 to 80 people and 365 day.