#include <bits/stdc++.h>

#define 	ll 						long double
#define 	pb 						push_back
#define 	mp 						make_pair
#define 	fast 					ios_base::sync_with_stdio(false);cin.tie(NULL);
#define 	ff 						first
#define 	ss 						second
#define 	nil 					-10e+9
#define 	initial 				0
#define 	waiting 				1
#define 	visit 					2
#define 	inf  					10e+9
#define 	mx   					200005
#define 	mxx  					1000005
#define 	mod  					1000000007
#define 	pr   					pair<ll,ll>
#define 	pp_queue 			priority_queue<pr,vector<pr>, greater<pr> >
#define 	dp_queue 			priority_queue<int,vector<int>, greater<int> >
#define 	sp_queue 			priority_queue<int>
#define 	fr(i,p,q)			for(int i=p;i<q;++i)
#define 	frr(i,p,q) 		for(int i=p;i<=q;++i)
#define 	mem(a,b) 			memset(a,b,sizeof(a))
#define 	len(a)   			(int)a.size()
#define 	input  				freopen("input.txt", "r", stdin);
#define 	output 				freopen("output.txt", "w", stdout);
#define 	debug(arr,j,n) fr(i,j,n) cout<<arr[i]<<" ";

ll power(ll a,ll b){ll aa=1;while(b){if(b&1){aa=aa*a;aa%=mod;}a=a*a;a%=mod;b/=2;}return aa;}

using namespace std;

int main()
{
  int n;
	cin>>n;
	ll a[n];
	fr(i,0,n) cin>>a[i];
	sort(a,a+n);


	ll deno=(a[0]+a[1])/2.0;

	fr(i,2,n){
		deno=(a[i]+deno)/2.0;
	}
	cout<<setprecision(15)<<deno<<"\n";

}
