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