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