浮点数二分

#include <bits/stdc++.h>
using namespace std;
int main(){
    double n;
    cin>>n;
    double l = -1e+8;
    double r = 1e+8;
    double mid;
    while(r-l>1e-8){
        mid = (l+r)/2;
        if(mid*mid*mid>=n){
            r = mid;
        }else{
            l = mid;
        }
    }
    printf("%.6lf",l);
}