#include <bits/stdc++.h>
using namespace std;
void print_vec(const vector<int> &v) {
  for (long long i = 0; i <= (long long)(v.size() - 1); i++) {
    if (i != 0) {
      cout << " ";
    }
    cout << v.at(i);
  }
  cout << endl;
}
int main() {
  int n;
  priority_queue<double, vector<double>, greater<double>> v;
  cin >> n;
  int inp;
  for (long long i = 0; i < (long long)(n); i++) {
    cin >> inp;
    v.push(inp);
  }
  while (v.size() > 1) {
    int r1 = v.top();
    v.pop();
    int r2 = v.top();
    v.pop();
    v.push((r1 + r2) / (double)2);
  }
  cout << v.top() << endl;
  return 0;
}
