#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  std::priority_queue<float, std::vector<float>, std::greater<float>> que;
  int N;
  cin >> N;
  for (int i = 0; i < N; i++) {
    int v;
    cin >> v;
    que.push(v);
  }
  for (int i = 0; i < N - 1; i++) {
    int v1, v2;
    v1 = que.top();
    que.pop();
    v2 = que.top();
    que.pop();
    que.push((float)(v1 + v2) / 2);
  }
  cout << que.top() << endl;
}
