defmodule Main do
  def main do
    {n, _} = IO.read(:line) |> Integer.parse()
    n |> solve |> IO.puts()
  end

  def solve(n), do: solve_rec(n, []) |> Enum.reverse() |> Enum.join()

  @alphabet ?A..?Z |> Enum.map(&[&1]) |> Enum.map(&to_string/1)
  @base @alphabet |> length

  def solve_rec(n, x) when n <= @base - 1, do: [n |> to_alphabet | x]

  def solve_rec(n, x),
    do: solve_rec(n |> rem(@base), [((n |> div(@base)) - 1) |> to_alphabet | x])

  def to_alphabet(n), do: @alphabet |> Enum.at(n)
end