#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  double a;
  vector<double> table;
  cin >> N;
  for (int i = 0; i < N; i++) {
    cin >> a;
    table.push_back(a);
  }
  for (int i = 0; i < N - 1; i++) {
    double min = *min_element(table.begin(), table.end());
    table.erase(min_element(table.begin(), table.end()));
    double min2 = *min_element(table.begin(), table.end());
    table.erase(min_element(table.begin(), table.end()));
    table.push_back((min + min2) / 2.0);
  }
  cout << table[0];
  return 0;
}
