#include <bits/stdc++.h>
using namespace std;
int main() {
  long long N;
  cin >> N;
  vector<double> v(N);
  for (long long i = 0; i < (long long)(N); i++) {
    cin >> v[i];
  }
  sort(v.begin(), v.end());
  reverse(v.begin(), v.end());
  stack<double> S;
  for (long long i = 0; i < (long long)(N); i++) {
    S.push(v[i]);
  }
  while (S.size() != 1) {
    long long a, b;
    a = S.top();
    S.pop();
    b = S.top();
    S.pop();
    S.push((double)(a + b) / 2);
  }
  cout << fixed << setprecision(100);
  cout << S.top() << endl;
}
