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