#include <bits/stdc++.h>
using namespace std;
const int MAXN = 51;
int n;
double v[MAXN];
void solve() {
  sort(v, v + n);
  double value = (v[0] + v[1]) / 2.0;
  for (int i = 2; i < n; i++) {
    value = (value + v[i]) / 2.0;
  }
  cout << setprecision(10) << value << endl;
}
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  solve();
}
