#include<bits/stdc++.h>
#define int long long
#define double long double
using namespace std;
const int inf=1e18;
int c;
double f(double x){
    double x5=x;
    for(int i=0;i<4;i++)x5*=x;
    return x5+x-c;
}
signed main(){
    cin>>c;
    double l=0,r=1e2;
    for(int i=0;i<100;i++){
        double mid=(l+r)/2;
        if(f(mid)<0)l=mid;
        else r=mid;
    }
    double lst=r;
    lst*=1000;
    int go=lst;
    cout<<fixed<<setprecision(3)<<(double)go/1000<<endl;
}