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

x = gets.to_i

def f (x, k)
     x 
end

loop { d, m = x.divmod 4; break if m != 0; x = d; };

3.step(x ** 0.5, 2) do |k|
    kk = k * k
    break if x < kk
    loop { d, m = x.divmod kk; break if m != 0; x = d; };
end

puts x