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