#include<bits/stdc++.h>
#define double long double
using namespace std;
const int N=1000010,mod=1e9+7;
const double eps=1e-12,ee=1e-10;
int n,a[N];
double b[N];
void sun(double r){for(int i=1;i<=n;i++)b[i]=2.0*asin((double)a[i]*0.5/r);sort(b+1,b+n+1);}
signed main(){
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		scanf("%d",&a[i]);
	}sort(a+1,a+n+1);
	double an1=-1,an2=-1;
	double ll=a[n]/2.0,rr=1e5;
	while(rr-ll>=eps){
		double r=(ll+rr)/2.0,su=0;
		sun(r);
		for(int i=1;i<=n;i++)su+=b[i];
		double j1=su-2.0*acos(-1);
		if(j1<0)rr=r;
		else ll=r;
	}
	sun(rr);double ss=0;
	for(int i=1;i<=n;i++)ss+=b[i];
	double j1=ss-2.0*acos(-1);
	if(j1>-ee&&j1<ee)an1=rr;
	ll=a[n]/2.0,rr=1e5;
	while(rr-ll>=eps){
		double r=(ll+rr)/2.0,su=0;
		sun(r);
		for(int i=1;i<n;i++)su+=b[i];
		double j2=b[n]-su;
		if(j2<0)rr=r;
		else ll=r;
	}
	sun(rr);ss=0;
	for(int i=1;i<n;i++)ss+=b[i];
	double j2=b[n]-ss;
	if(j2>-ee&&j2<ee)an2=rr;
	if(an1==-1.0)cout<<setprecision(10)<<fixed<<an2;
	if(an2==-1.0)cout<<setprecision(10)<<fixed<<an1;
}