#include<bits/stdc++.h>
using namespace std;using ld=long double;using ll=long long;
using pll=pair<ll,ll>;
const int M=998244353,inv2=(M+1)/2,P=20;const ld eps=1e-8,pi=acos(-1);
ll poww(ll bs,ll x){ll res=1;for(;x;x>>=1,(bs*=bs)%=M)if(x&1)(res*=bs)%=M;return res;}
ll invv(ll bs){return poww(bs,M-2);}
struct S
{
    int n,mx=0;vector<int>a;
    ld trial2(ld x)
    {
        ld sum=0;
        for(auto&k:a)
        {
            if(k==mx)sum-=asin(k/x);
            else sum+=asin(k/x);
        }
        return sum;
    }
    ld trial(ld x)
    {
        ld sum=0;
        for(auto&k:a)
        {
            if(abs(k-x)<eps)sum+=pi/2;
            else if(k>x)return 10;
            else sum+=asin(k/x);
        }
        return sum;
    }
    void ini()
    {
        cin>>n;a.resize(n);for(auto&k:a)cin>>k,mx=max(mx,k);
        ld sum=trial(mx);if(abs(sum-pi)<eps){cout<<mx/2.0<<'\n';return;}
        if(sum>pi)
        {
            //cout<<"A\n";
            ld L=mx,R=1e7;
            while(R-L>eps)
            {
                ld x=(L+R)/2,sum=trial(x);

                //cout<<x<<'/'<<sum<<'\n';
                sum>pi?L=x:R=x;
            }
            cout<<R/2<<'\n';
        }
        else
        {
            ld L=mx,R=1e7;
            while(R-L>eps)
            {
                ld x=(L+R)/2,sum=trial2(x);

                //cout<<x<<'/'<<sum<<'\n';
                sum<0?L=x:R=x;
            }
            cout<<R/2<<'\n';
        }
    }
    void solve()
    {

    }
};
signed main()
{
    cout<<fixed<<setprecision(12);
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t=1;//cin>>t;
    while(t--){S SS;SS.ini();SS.solve();}
}
/*
1274368 996265816
1807139^
1274369 996265816
1165429^
1274369 996269373
inf^
 */