#!/usr/bin/env ruby

require "openssl"

len = ARGV[0].to_i
if len == 0
  len = 8
end

str = ""

while str.length < len
  while str.length < len
    chr = OpenSSL::Random.random_bytes(1)
    ord = chr.unpack('C')[0]

    #          0            9              a            z
    if (ord >= 48 && ord <= 57) || (ord >= 97 && ord <= 122)
      # avoid ambiguous characters
      next if chr == "0" || chr == "l"

      str << chr
    end
  end
end

puts str