#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pli = pair<ll, int>;
const int INF = 0x3f3f3f3f, N = 2e5 + 5;
const ll LINF = 1e18 + 5;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  priority_queue<double, vector<double>, greater<double>> q;
  for (int i = 1; i <= n; i++) {
    double v;
    cin >> v;
    q.push(v);
  }
  while ((int)q.size() >= 2) {
    auto u = q.top();
    q.pop();
    auto v = q.top();
    q.pop();
    q.push((u + v) / 2);
  }
  auto ans = q.top();
  cout << fixed << setprecision(12) << ans;
  return 0;
}
