Broadcast Appeal Score

A broadcast message is analyzed by looking at every contiguous substring. The appeal of a substring is the number of distinct characters present inside that substring. For example, repeated copies of the same character inside one substring contribute only once to that substring's appeal. The final broadcast appeal score is the sum of appeal values over all possible non-empty substrings of the message. Input Format: You are given a lowercase string message. Output Format: Return the total appeal score across all substrings of message.