#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<float> vec(N);
  for (int i = 0; i < N; i++) {
    cin >> vec.at(i);
  }
  int i = 0;
  while (i < N - 1) {
    sort(vec.begin(), vec.end());
    vec.at(0) = vec.at(0) / 2 + vec.at(1) / 2;
  }
  cout << vec.at(0) << endl;
}
