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