#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
int main() {
  int N;
  cin >> N;
  vector<int> V(N);
  for (int i = 0; i < (N); i++) cin >> V[i];
  sort(V.begin(), V.end());
  double ans = (V[0] + V[1]) / 2;
  for (int i = 2; i < N; i++) {
    if (ans > V[i] && i != N - 1) {
      double x = V[i + 1];
      V[i + 1] = ans;
      ans = x;
    }
    ans = (ans + V[i]) / 2;
  }
  cout << setprecision(5) << ans << endl;
}
