#include <map>
#include <cmath>
#include <queue>
#include <cstdio>
#include <vector>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#define MAX_N 105

using namespace std;

int main()
{
    //freopen("in.txt", "r", stdin);

    int N;
    double a[MAX_N];
    scanf("%d", &N);
    for (int i = 0; i < N; i++)
        scanf("%lf", &a[i]);
    sort(a, a + N);

    if (N == 1)
        printf("%.3f\n", a[0]);
    else if (N == 2)
        printf("%.3f\n", 2 * sqrt(a[0] * a[1]));
    else
    {
        double ans = 2 * sqrt(a[N - 1] * a[N - 2]);
        for (int i = N - 3; i >= 0; i--)
        {
            ans = 2 * sqrt(ans * a[i]);
        }
        printf("%.3f\n", ans);
    }
    return 0;
}
只用排序一次不就好了吗0.0