6.数的三次方根

#include <bits/stdc++.h>
using namespace std;
int main () {
    double n;
    cin >> n;
    double l = -100, r = 100;
    while (r - l > 1e-8) { //当区间足够小的时候 
        double mid = (l + r) / 2;
        if (mid * mid * mid >= n) {
            r = mid;
        } else {
            l = mid;
        }
    }
    cout << fixed << setprecision(6) << l << endl;
    return 0;
}