#include <iostream>
#include <iomanip>


double good(int a, int b, int c, int d, double mid){
    return a * mid * mid * mid + b * mid * mid + c * mid + d;
}

double bin(int a, int b, int c, int d){
    double left = -1e9, right = 1e9, mid;
    while(left + 1e-5 < right){
        mid = (left + right) / 2;
        if (good(a, b, c, d, mid) <= 0)
            left = mid;
        else
            right = mid;
    }
    return (left + right) / 2;
}


int main (){
    int a, b, c, d;
    std::cin >> a >> b >> c >> d;
    if (a < 0){
        a = -a;
        b = -b;
        c = -c;
        d = -d;
    }
    std::cout << std::setprecision(10) << bin(a, b, c , d);


    return 0;
}