#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int INF = 999999999;
int main() {
  int N;
  cin >> N;
  deque<double> v;
  for (int i = 0; i < N; ++i) {
    double inp;
    cin >> inp;
    v.push_back(inp);
  }
  while (v.size() != 1) {
    sort(v.begin(), v.end());
    double fnum = v.front();
    double bnum = v.back();
    double anum = (fnum + bnum) / 2.0;
    v.pop_front();
    v.pop_back();
    v.push_back(anum);
  }
  cout << v[0] << endl;
}
