#include <iostream>
using namespace std;
int main(){
double n;
cin >> n;
double l = -10000, r = 10000;
while(r - l > 1e-8) {
double m = (r + l) / 2.;
if(m * m * m <= n) {
l = m;
}else {
r = m;
}
}
printf("%.6f", r);
return 0;
}