#include <iostream>

#define abs(x) ( x>0.000000 ? x : -x )

double third_root( double x, double q) {
	double x2 = x - (x*x*x - q)/( 3 * x*x );
	if( abs( x2*x2*x2 - q )<0.00001*q ) return x2;
	return third_root( x2, q);
}

int main() {
	int n;
	while( std::cin >> n) {
		std::cout << third_root( (double)n / 2.0, (double)n ) << std::endl;
	}
	return 0;
}