class Yukicoder
  def initialize
    n = gets.to_i
    answer = ""

    while (answer.empty? && n > 25) || n > 26
      i = n % 26
      n /= 26
      answer += (i+10).to_s(36).upcase
    end

    if answer.empty?
      answer += (n+10).to_s(36).upcase
    else
      answer += (n+9).to_s(36).upcase
    end

    puts answer.reverse
  end
end

Yukicoder.new