#include<iostream>
#include<algorithm>
using namespace std;
long long n;
const double eps=1e-6;
bool check(double m){
	if(m*m*m>=n)  return 1;
	return 0;
}
long long search(double l,double r){
	while(r-l>eps){
		double mid=(l+r)/2;
		if(check(mid))  r=mid;
		else l=mid;
	}
	return l;
}
int main(){
	cin>>n;
	cout<<search(0,n)<<endl;
	return 0;
}