#include <bits/stdc++.h>
using ll = long long;
using namespace std;
using pii = pair<int, int>;
int n;
double v;
priority_queue<double, vector<double>, greater<double>> q;
void input() {
  cin >> n;
  for (int i = 0, i_len = (n); i < i_len; ++i) {
    cin >> v;
    q.push(v);
  }
}
void src() {
  for (int c = 0, c_len = (n - 1); c < c_len; ++c) {
    int v1 = q.top();
    q.pop();
    int v2 = q.top();
    q.pop();
    q.push((v1 + v2) / 2.0);
  }
  cout << setprecision(10) << fixed << q.top();
  return;
}
int main(int argc, char* argv[]) {
  input();
  src();
  return 0;
}
