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