#include <bits/stdc++.h>
using ll = long long;
using namespace std;
const int INF = 1e9 + 5;
const ll INFF = 1e18 + 5;
const int M = 1e9 + 7;
const double pi = acos(-1);
int main() {
  cin.tie(0);
  cout.tie(0);
  ios_base::sync_with_stdio(0);
  int n;
  cin >> n;
  priority_queue<double> pq;
  vector<int> a(n);
  for (int& x : a) {
    cin >> x;
    pq.push(-x);
  }
  for (int i = 1; i <= n - 1; ++i) {
    int u, v;
    u = pq.top();
    pq.pop();
    v = pq.top();
    pq.pop();
    u = -u;
    v = -v;
    pq.push(-(u + v) / 2.00);
  }
  double x = -pq.top();
  pq.pop();
  printf("%.6lf", x);
  return 0;
}
