# include <bits/stdc++.h>
using namespace std;
int id[30];
double f[5000000],a[30],b[30];
int main()
{
	int n;
	cin>>n;
	for(int i=0;i<n;i++) scanf("%lf",&a[i]);
	for(int i=1;i<(1<<n);i++)
	{
		vector<int> legal;
		for(int j=0;j<n;j++)
			if((i>>j)&1) legal.push_back(j);
		double mx=0;
		for(int j:legal) b[j]=f[i^(1<<j)],mx=max(mx,min(a[j],b[j]));
		double K=0,B=0;
		int cnt=0;
		for(int j:legal)
			if(a[j]>b[j]) id[++cnt]=j;
		sort(id+1,id+cnt+1,[](int i,int j){return a[i]>a[j];});
		id[cnt+1]=n;
		for(int j=1;j<=cnt;j++)
		{
			K+=1/(a[id[j]]-b[id[j]]);B+=a[id[j]]/(a[id[j]]-b[id[j]]);
			double x=(B-1)/K;
			if(x>=a[id[j+1]]){mx=max(mx,x);break;}
		}
		K=B=0;cnt=0;
		for(int j:legal)
			if(a[j]<b[j]) id[++cnt]=j,B+=1;
		sort(id+1,id+cnt+1,[](int i,int j){return b[i]>b[j];});
		id[cnt+1]=n;
		for(int j=1;j<=cnt;j++)
		{
			K+=1/(b[id[j]]-a[id[j]]);B-=1+a[id[j]]/(b[id[j]]-a[id[j]]);
			double x=(1-B)/K;
			if(x>=b[id[j+1]]){mx=max(mx,x);break;}
		}
		f[i]=mx;
	}
	printf("%.10lf\n",f[(1<<n)-1]);
	return 0;
}