Given a string s, return the number of distinct substrings of s.

A substring of a string is obtained by deleting any number of characters (possibly zero) from the front of the string and any number (possibly zero) from the back of the string.

 

Example 1:

Input: s = "aabbaba"
Output: 21
Explanation: The set of distinct strings is ["a","b","aa","bb","ab","ba","aab","abb","bab","bba","aba","aabb","abba","bbab","baba","aabba","abbab","bbaba","aabbab","abbaba","aabbaba"]

Example 2:

Input: s = "abcdefg"
Output: 28

 

Constraints:

• 1 <= s.length <= 500
• s consists of lowercase English letters.

 

Follow up: Can you solve this problem in O(n) time complexity?