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