#include <iostream>
#include <cmath>
#include <cstdlib>
using namespace std;

int Comp(const void *a, const void *b)
{
    return *(double*)a - *(double*)b;
}

int main()
{
    int n = 0, i;
    double * mas = new double[n];

    cin >> n;

    for(i = 0; i < n; i++)
        cin >> mas[i];

    qsort(mas, n, sizeof(double), Comp);

    for(i--; i > 0; i--)
    {
        mas[i - 1] = 2 * sqrt(mas[i - 1] * mas[i]);
        qsort(mas, i - 1, sizeof(double), Comp);
    }

    printf("%.2f", mas[0]);
}