#include<bits/stdc++.h>
using namespace std;
#define N 22
typedef long long ll;
int n;
double dp[1<<N],a[N];
double calc(const vector<double> &a,const vector<double> &b){ // min_p{max_i{(1-p[i])*a[i]+p[i]*b[i]}}
	if(a[0]<=b[0])return a[0];
	double sum=1.0/(a[0]-b[0]),P=0;
	for(int i=1;i<(int)a.size();++i){
		double need=(a[i-1]-a[i])*sum;
		if(P+need>1){
			return a[i-1]-(1-P)/sum;
		}
		if(a[i]<=b[i])return a[i];
		sum+=1.0/(a[i]-b[i]);
		P+=need;
	}
	return a.back()-(1-P)/sum;
}
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.setf(ios::fixed);
	cout.precision(10);
	cin>>n;
	for(int i=0;i<n;++i){
		cin>>a[i];
	}
	sort(a,a+n,greater<double>());
	for(int s=1;s<(1<<n);++s){
		vector<double> A,B;
		A.reserve(n),B.reserve(n);
		for(int i=0;i<n;++i){
			if(s>>i&1){
				A.push_back(a[i]);
				B.push_back(dp[s^(1<<i)]);
			}
		}
		dp[s]=calc(A,B);
	}
	cout<<dp[(1<<n)-1]<<'\n';
	return 0;
}