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