#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  if (n == 2) {
    cout << (v[0] + v[1]) / 2 << endl;
    return 0;
  }
  sort(v.begin(), v.end());
  int ans = (v[0] + v[1]) / 2;
  for (int i = 0; i < n - 2; i++) {
    ans = (ans + v[i + 2]) / 2;
  }
  cout << ans + 0.5 << endl;
}
