test9

#include <iostream>
#include <iomanip>
#include <stdio.h>

using namespace std;

int main(){
    short a = 0,b = 0,c = 0,d = 0;
    long double x;
    freopen("cubroot.in", "r", stdin);
    freopen("cubroot.out", "w", stdout);
    cin>>a>>b>>c>>d;
    if (a < 0){
        a*=-1;
        b*=-1;
        c*=-1;
        d*=-1;
    }

    long double l = -1e6;
    long double r = 1e6;

    for(int i = 0; i < 100; ++i){
        long double midl = (l + r)/2;
        if((a*midl*midl*midl + b*midl*midl + c*midl + d) < 0){
            l = midl;
        }else{
            r = midl;
        }
        x = l;
    }

//    printf("%.6llf\n", x);
   cout << x;

    

    return 0;
}