###  this is the input
###
###

_____  put a row of underscores stretching one character off either side on top
 ###
 ###
 ###

   _____  put a diagonal of slashes in front going the height of the input
  / ###
 /  ###
/   ###

      _____ put a diagonal of backslashes in front of that, going up half of the input's height rounded up
     / ###
   /  ###
  /   ###

Input:
40
Output:
  ____
/ 40

Input:
  ____
/ 40
Output:
   _______
  /   ____
/  / 40

Input:
/|
 |
 |
_|_
Output:
      _____
     / /|
    /   |
  /    |
 /    _|_

Input:
#  #
#  #
#####
   #
   #
Output:
        _______
       / #  #
      /  #  #
    /   #####
   /       #
  /        #