#include <bits/stdc++.h>
using namespace std;
int main() {
  priority_queue<double, vector<double>, greater<double> > a;
  int n, m;
  while (cin >> n) {
    for (int i = 0; i < n; i++) {
      cin >> m;
      a.push(m);
    }
    for (int i = 1; i < n; i++) {
      int temp1, temp2;
      double temp3;
      temp1 = a.top();
      a.pop();
      temp2 = a.top();
      a.pop();
      temp3 = (double)(temp1 + temp2) / 2.0;
      a.push(temp3);
    }
    cout << a.top() << endl;
    a.pop();
  }
  return 0;
}
