A = gets.to_i

def f(e)
  return A if e == 1

  ok = A
  ng = 0

  while (ok - ng).abs > 1
    x = (ok + ng) / 2

    if A <= x ** e
      ok = x
    else
      ng = x
    end
  end

  ok
end

ans = A

2.upto(110) do |e|
  v = e * f(e)
  ans = v if ans > v
end

puts ans