defmodule Main do
  def main do
    n = IO.gets("") |> String.trim |> String.to_integer
    numbers = 1..n
    Enum.to_list(numbers)
    IO.puts(Enum.map(numbers, fn x -> x * x end) |> Enum.filter(fn(x) -> x <= n end) |> Enum.max)
  end
end
