#include <bits/stdc++.h>
using namespace std;
int N, M, K;
int main() {
  cin >> N;
  vector<int> R;
  for (int i = 0; i < N; i++) {
    int tmp;
    cin >> tmp;
    R.push_back(tmp);
  }
  sort(R.begin(), R.end());
  float ans = (R[0] + R[1]) / 2;
  if (N >= 3) {
    for (int i = 2; i < N; i++) {
      ans = (ans + R[i]) / 2;
    }
  }
  cout << ans << endl;
}
