#include <bits/stdc++.h>
using namespace std;
float average(int x, int y) {
  float ret;
  ret = (x + y) / 2.0;
  return ret;
}
int main() {
  int N, tmp;
  cin >> N;
  vector<float> V(N);
  for (int i = 0; i < N; i++) {
    cin >> tmp;
    V.at(i) = (float)tmp;
  }
  sort(V.begin(), V.end());
  for (int i = 0; i < N - 1; i++) {
    V.at(i + 1) = average(V.at(i), V.at(i + 1));
  }
  cout << V.at(N - 1) << endl;
}
