#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int n, i, j;
  long long int a, b;
  double c;
  cin >> n;
  priority_queue<double, vector<double>, greater<double>> q;
  for (i = 0; i < n; i++) {
    cin >> j;
    q.push(j);
  }
  while (q.size() > 1) {
    a = q.top();
    q.pop();
    b = q.top();
    q.pop();
    c = (a + b) / 2.0;
    q.push(c);
  }
  cout << q.top();
  return 0;
}
