/*
tetration

tetration(a,n)=a^a^⋅⋅⋅^a (n times).
Very quickly, Anthony becomes interested in infinite tetrations, 
namely
tetration(a,∞)=a^a^⋅⋅⋅∞ times.
Anthony wonders, given an arbitrary real number N, what is the 
solution to tetration(a,∞)=N? Unable to figure it out, Anthony has 
asked you to write a program to help him!

Here’s a fun fact: A solution only exists for 1/e≤N≤e.

Input
The first line of input contains one real number N, 0.36788≤N≤2.718281.

Output
Output a single line containing a real number a, such that 
tetration(a,∞) =N. Your answer will be considered correct if its 
absolute or relative error doesn’t exceed 1e−5.
*/

#include <iostream>
#include <cmath>

int main() {
	double N{ 0 };
	std::cin >> N;
	std::cout << pow(N,1/N);
}