#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vl>;
using pll = pair<ll, ll>;
using vb = vector<bool>;
const ll oo = 0x3f3f3f3f3f3f3f3fLL;
const double eps = 1e-9;
int main() {
  ll n;
  cin >> n;
  double sum = 0;
  cin >> sum;
  for (ll i = (0); i < (ll)(n - 1); i++) {
    double z;
    cin >> z;
    sum = (sum + z) / 2;
  }
  cout << sum << endl;
}
