class Yukicoder
  LIST = [*('0'..'9')] + [*('A'..'Z')]

  def initialize
    n = gets.chomp.to_i
    num_list = []
    max_value = 0

    n.times do
      str = gets.chomp
      num_list << str

      max_value = [max_value, str.chars.map{|ch| LIST.index(ch)}.max].max
    end

    puts num_list.map{|num| encode(num, max_value+1)}.min
  end

  def encode(str, e)
    str.to_i(e)
  end
end

Yukicoder.new