#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  priority_queue<int, vector<int>, greater<int>> pq;
  for (int i = 0; i < n; i++) {
    int a;
    cin >> a;
    pq.push(a);
  }
  double value;
  while (!pq.empty()) {
    int x, y;
    value = 0;
    x = pq.top();
    pq.pop();
    y = pq.top();
    pq.pop();
    value = (double)(x + y) / 2;
    if (!pq.empty()) {
      pq.push(value);
    }
  }
  cout << value << endl;
}
