#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  double make;
  vector<int> rare(N);
  for (int i = 0; i < N; i++) {
    cin >> rare.at(i);
  }
  for (int i = 0; i < N - 1; i++) {
    sort(rare.begin(), rare.end());
    make = (rare.at(0) + rare.at(1)) / 2;
    rare.push_back(make);
    reverse(rare.begin(), rare.end());
    rare.pop_back();
    rare.pop_back();
  }
  cout << rare.at(0) << endl;
}
