#include <bits/stdc++.h>
using namespace std;
int main() {
  long long N;
  cin >> N;
  double v[N];
  double kotae = 0.0;
  for (int i = 0; i < N; i++) {
    cin >> v[i];
  }
  sort(v, v + N);
  double k;
  for (int i = 1; i < N; i++) {
    k = (v[i - 1] + v[i]) / 2.0;
    kotae += k;
    v[i] = kotae;
  }
  cout << k << endl;
}
