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