Common Tail
You are given two lists of integers. Elements are unique inside each list. These lists may have common element(s). But we are interested in the common element(s) at the end of the lists. Your function should return an element, from what a common part starts and there are no different element(s) after this part - the first element of the last common part (common tail). If there is no such element (lists don't end with common element) your function should return None. Good luck!
Input: Two lists of integers.
Output: Integer or None.
Examples:
assert common_tail([], [1, 2, 3]) == None assert common_tail([1], [1]) == 1 assert common_tail([3], [1, 2, 3]) == 3 assert common_tail([1, 3, 4, 6], [2, 9, 4, 6]) == 4
