Process String with Special Operations I

Description

You are given a string s consisting of lowercase English letters and the special characters: *, #, and %.

Build a new string result by processing s according to the following rules from left to right:

- If the letter is a lowercase English letter append it to result.

- A '*' removes the last character from result, if it exists.

- A '#' duplicates the current result and appends it to itself.

- A '%' reverses the current result.

Return the final string result after processing all characters in s.