代码：

#include<iostream>
#include<cstdio>
using namespace std;
int main(){
    double n;
    scanf("%lf",&n);
    double l=-10000;
    double r=10000;
    while(r-l>=1e-7){//!!!!!!!!!!!!!!!!!!1
        double mid=(l+r)/2;
        if(mid*mid*mid>=n)
        r=mid;//!!!!!!!!!!!!!!
        else
        l=mid;//!!!!!!!!!!!!!!

    }
    printf("%lf",l);
    return 0;
}