LEAP YEAR
Write a function that returns true or false depending on whether its input integer is a leap year or not.
A leap year is divisible by 4, but is not otherwise divisible by 100 unless it is also divisible by 400.
- 2001 is a typical common year
- 1996 is a typical leap year
- 1900 is an atypical common year
- 2000 is an atypical leap year