一定要考虑好变量的类型, 避免低级错误
#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
using namespace std;
double n;
double f(double d){
return d * d * d;
}
int main(){
cin >> n;
double l = -100, r = 100;
while(r - l > 1e-8){
double m = (l + r) / 2;
if(f(m) <= n) l = m;
else r = m;
}
printf("%lf", r);
}