First off, leap years are not being considered for this. In fact the year that people are born shouldn't be taken into consideration, for simplicity.
The basic question is given an input, a single integer representing the number of people in the room (X >= 1). Return the probability that 2 or more people share the same birthday.
The return from the function should be a value between 0 and 1, inclusive. It should also be rounded out to the 10 thousandth decimal point (4 after the decimal point). There should be no trailing zeros included.