Create a routine that, given a set of strings representing directory paths and a single character directory separator, will return a string representing that part of the directory tree that is common to all the directories.

Test your routine using the forward slash '/' character as the directory separator and the following three strings as input paths:
  '/home/user1/tmp/coverage/test'
  '/home/user1/tmp/covert/operator'
  '/home/user1/tmp/coven/members'

Note: The resultant path should be the valid directory <code>'/home/user1/tmp'</code> and not the longest common string <code>'/home/user1/tmp/cove'</code>.<br>
If your language has a routine that performs this function (even if it does not have a changeable separator character), then mention it as part of the task.


;Related tasks
* [[Longest common prefix]]

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