POJ 1862

#include <iostream>
#include <algorithm>
#include <iomanip>
#include <cmath>
#define MAXN 100
using namespace std;

double _m[MAXN];

double fun();

int n;

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

    int i;
    cin>>n;
    for(i = 0; i < n; ++ i)
    {
        cin>>_m[i];
    }
    
    double tem = fun();

    for(i = 1; i < n; ++ i)
    {
        tem = 2*sqrt(fun()*tem);
    }
    cout<<setiosflags(ios::fixed)<<setprecision(3)<<tem<<endl;
}

double fun()
{
    int i;
    double max = -1;
    int index;
    for(i = 0; i < n; ++ i)
    {
        if(_m[i] > max)
        {
            max = _m[i];
            index = i;
        }
    }
    _m[index] = -1;    
    return max;
}