#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<int> h(N);
  for (int i = 0; i < (N); ++i) cin >> h[i];
  double ans = h[0];
  cout << fixed << setprecision(6);
  sort(h.begin(), h.end());
  for (int i = 1; i < N; i++) {
    ans = (double)((ans + h[i]) / 2);
  }
  cout << (double)ans << endl;
  return 0;
}
