import java.util.;
import java.io.;
public class Main{
public static void main(String[] args)throws Exception{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
double n = Double.parseDouble(br.readLine());
BinarySearch(n);
}
public static void BinarySearch(double target){
double left = -10000;
double right = 10000;
while(right - left > 1e-8){
double mid = left + (right - left) / 2;
if(mid * mid *mid < target){
left = mid;
}else{
right = mid;
}
}
System.out.printf("%.6f",right);
}
}