3324. Find the Sequence of Strings Appeared on the Screen

You are given a string target. Alice is going to type target on her computer using a special keyboard that has only two keys: - Key 1 appends the character "a" to the string on the screen. - Key 2 changes the last character of the string on the screen to its next character in the English alphabet. For example, "c" changes to "d" and "z" changes to "a". Note that initially there is an empty str