#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  double B;
  vector<double> u(5);
  for (int i = 0; i < N; i++) {
    cin >> u.at(i);
  }
  double A = u.at(0);
  sort(u.begin(), u.end());
  for (int i = 0; i < N; i++) {
    A += u.at(i);
    B = A / 2;
  }
  cout << B << endl;
}
