#! ruby
# yukicoder My Practice
# author: Leonardone @ NEETSDKASU

x = gets.to_i

def f (x, k)
    loop { d, m = x.divmod k; break if m != 0; x = d; }; x 
end

x = f(x, 4)

3.step(x ** 0.5, 2) do |k|
    kk = k * k
    break if x < kk
    x = f(x, kk)
end

puts x