servername.rb

def partner_server(name)
  # takes a server name and returns the previous server if even
  # the next server if odd
  server = name.scan(/\d+/).first
  length = server.length
  number = server.to_i
  if number.to_i.odd?
    number += 1
  else
    number -= 1
  end
  partner_name = name.sub(server, number.to_s.rjust(length,'0'))
end

puts partner_server(ARGV[0])