#include <bits/stdc++.h>
using namespace std;
priority_queue<int, vector<int>, greater<int> > q;
int main() {
  int n;
  cin >> n;
  double x, y, z;
  for (int i = 0; i < n; i++) {
    cin >> x;
    q.push(x);
  }
  while (q.size() >= 2) {
    x = q.top();
    q.pop();
    y = q.top();
    q.pop();
    z = (x + y) / 2;
    q.push(z);
  }
  double p = q.top();
  printf("%.7lf", p);
  return 0;
}
