#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using p = pair<int, int>;
const long long INF = 1ll << 60;
int main() {
  int N;
  cin >> N;
  vector<int> v(N);
  for (int i = 0; i < (int)(N); i++) cin >> v[i];
  sort(v.begin(), v.end());
  double ans = INF;
  for (int i = 0; i < (int)(N - 1); i++) {
    ans = (double)(v[i] + v[i + 1]);
    ans /= 2;
    v[i + 1] = ans;
  }
  cout << fixed << setprecision(15) << ans << endl;
  return 0;
}
