#include <algorithm>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <numbers>
#define double long double
template<typename T>
T sqr(T a) { return a * a; }
constexpr int N = 1000, X = 6000;
constexpr double eps = 1E-9;
int x[N];
int main()
{
    int n; std::cin >> n;
    for (int i = 0; i < n; ++i)
        std::cin >> x[i];
    double l = static_cast<double>(*std::max_element(x, x + n)) / 2, r = N * X;
    auto calc = [&](double r) {
        double res = 0;
        for (int i = 0; i < n; ++i)
            res += std::acos(std::clamp(1 - sqr(x[i]) / (2 * sqr(r)), -1.l, 1.l));
        return res;
    };
    if (calc(l) + eps > 2 * std::numbers::pi)
    {
        for (int i = 60; i--; )
        {
            double m = (l + r) / 2;
            if (calc(m) > 2 * std::numbers::pi)
                l = m;
            else
                r = m;
        }
    }
    else
    {
        int j = std::max_element(x, x + n) - x;
        auto calc = [&](double r) {
            double res = 0;
            for (int i = 0; i < n; ++i)
            {
                double term = std::acos(std::clamp(1 - sqr(x[i]) / (2 * sqr(r)), -1.l, 1.l));
                if (i == j) res += term;
                else res -= term;
            }
            return res;
        };
        for (int i = 60; i--; )
        {
            double m = (l + r) / 2;
            if (calc(m) > 0)
                l = m;
            else
                r = m;
        }
    }
    std::cout << std::fixed << std::setprecision(8) << l << "\n";
}