#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <sstream>
#include <bitset>
 
#define INPUT_FROM_FILE (0) 
#if INPUT_FROM_FILE
#include <fstream>
#endif


int main(int argc, char **argv){
	int q;

#if INPUT_FROM_FILE
	std::ifstream ifs("test.txt");
	//FILE *fp = fopen("test.txt", "r");
#endif

#if INPUT_FROM_FILE
	while(ifs >> q){
#else
	while(std::cin >> q){
#endif
		if(q == -1){ break; }
		double pre_x = 0.5 * q;
		double cur_x = 0;
		double cr = 0.00001 * q;

		while(fabs(pow(cur_x, 3) - q) >= cr){
			double pre_x2 = pre_x * pre_x;
			double pre_x3 = pre_x2 * pre_x;

			cur_x = pre_x - (pre_x3 - q) / (3 * pre_x2);
			pre_x = cur_x;
		}
		printf("%.6lf\n", cur_x);
	}


 
#if INPUT_FROM_FILE
	//fclose(fp);
#endif
    return 0;
}
