A string is said to be a special string if either of two conditions is met:
All of the characters are the same, e.g. aaa.
All characters except the middle one are the same, e.g. aadaa.
A special substring is any substring of a string which meets one of those criteria. Given a string, determine how many special substrings can be formed from it.
For example, given the string s= mnonopoo, we have the following special substrings: