Switcharoo

Create a function that takes a string and returns a new string with its first and last characters swapped, except under three conditions:

1. If the length of the string is less than two, return "Incompatible.".
2. If the argument is not a string, return "Incompatible.".
3. If the first and last characters are the same, return "Two's a pair.".

Examples

flip_end_chars("Cat, dog, and mouse.") ➞ ".at, dog, and mouseC"

flip_end_chars("ada") ➞ "Two's a pair."

flip_end_chars("Ada") ➞ "adA"

flip_end_chars("z") ➞ "Incompatible."

flip_end_chars([1, 2, 3]) ➞ "Incompatible."

Notes

Tests are case sensitive (e.g. "A" and "a" are not the same character).