#include <cstdio>
#include <iostream>
using namespace std;

int main() {
    double s;
    cin>>s;
    double l = -20,r = 20;
    while(r-l>1e-8){
       double mid = (l+r)/2;
       if(mid*mid*mid>=s) r = mid;
       else l = mid;
    }
    printf("%.1lf",l);
}
// 64 位输出请用 printf("%lld")