#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vb = vector<bool>;
using vll = vector<ll>;
using vd = vector<double>;
using vvi = vector<vi>;
using vvb = vector<vb>;
constexpr int MOD = 1000000007;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  priority_queue<double> q;
  for (int i = 0; i < (int)(n); ++i) {
    double a;
    cin >> a;
    q.push(-a);
  }
  while (q.size() >= 1) {
    double a = -q.top();
    q.pop();
    double b = -q.top();
    q.pop();
    q.push(-(a + b) / 2);
  }
  cout << -q.top() << endl;
  return 0;
}
