You are given a string and two markers (the initial and final). You have to find a substring enclosed between these two markers. But there are a few important conditions:

• The initial and final markers are always different.
• If there is no initial marker then the beginning should be considered as the beginning of a string.
• If there is no final marker then the ending should be considered as the ending of a string.
• If the initial and final markers are missing then simply return the whole string.
• If the final marker is standing in front of the initial one then return an empty string.

Input: Three arguments. All of them are strings. The second and third arguments are the initial and final markers.

Output: A string.

between_markers('What is >apple<', '>', '<') == 'apple'
between_markers('No[/b] hi', '[b]', '[/b]') == 'No'

How it is used: for parsing texts

Precondition: can't be more than one final marker and can't be more than one initial