#include <bits/stdc++.h>
using namespace std;
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;
  ans = (V[0] + V[1]) / 2;
  for (int i = 2; i < N; i++) {
    ans = (ans + V[i]) / 2;
  }
  cout << ans << endl;
  return 0;
}
