#include <bits/stdc++.h>
#define rep(i,x,n) for(int i = x; i < (int)(n); i++)
#define rep_ll(i,x,n) for(ll i = x; i < (ll)(n); i++)
using namespace std;
typedef long long ll;
typedef unsigned long long u_ll;
typedef pair<int, int> pair_;
const long double PI = (acos(-1));
const int INF = 1001001001;
const int dx[] = {-1, 0, 1, 0}; const int dy[] = {0, -1, 0, 1};
ll mod = 1000000007;
int main(){
    int n;
    cin >> n;
    priority_queue<double> v;
    double x;
    rep(i, 0, n) {
        cin >> x;
        v.push(x);
    }
    rep(i, 0, n-1){
        double xx = v.top();
        v.pop();
        double yy = v.top();
        v.pop();
        v.push((xx+yy)/2);
    }
    double ans=v.top();
    cout << fixed << precision(6) << ans;
}