#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<double> x(n);
  for (int i = 0; i < n; i++) {
    cin >> x.at(i);
  }
  for (int i = 0; i < n - 1; i++) {
    if (x.at(0) == 1001 || x.at(1) == 1001) {
      break;
    }
    double y = 0;
    sort(x.begin(), x.end());
    y = (x.at(0) + x.at(1)) / 2;
    x.at(0) = 1001;
    x.at(1) = 1001;
    x.push_back(y);
  }
  sort(x.begin(), x.end());
  cout << x.at(0) << endl;
}
