Given an integer n, return the number of strings of
length n that consist only of vowels
(a, e, i, o, u)
and are lexicographically sorted.
A string s is lexicographically sorted if for all valid
i, s[i] is the same as or comes before s[i+1]
in the alphabet.
Example 1:
Input: n = 1
Output: 5
Explanation: The 5 sorted strings that consist of vowels only are ["a","e","i","o","u"].
Example 2:
Input: n = 2 Output: 15 Explanation: The 15 sorted strings that consist of vowels only are ["aa","ae","ai","ao","au","ee","ei","eo","eu","ii","io","iu","oo","ou","uu"]. Note that "ea" is not a valid string since 'e' comes after 'a' in the alphabet.
Example 3:
Input: n = 33 Output: 66045
Constraints:
1 <= n <= 50