#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int N;
  double v;
  priority_queue<long long int, vector<long long int>, greater<long long int> >
      que;
  double res = 0;
  cin >> N;
  for (int i = 0; i < N; i++) {
    cin >> v;
    que.push(v);
  }
  while (que.size() != 1) {
    double a, b;
    a = que.top();
    que.pop();
    b = que.top();
    que.pop();
    res = (a + b) / 2.0;
    que.push(res);
  }
  cout << res << endl;
  return 0;
}
