#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9;
const int MOD = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void solve() {
  long long n;
  cin >> n;
  set<long double> q;
  for (long long i = 0; i < n; ++i) {
    long long x;
    cin >> x;
    q.insert((long double)(x));
  }
  while (q.size() != 1) {
    long double tmp = *q.begin() + *next(q.begin());
    q.erase(q.begin());
    q.erase(q.begin());
    tmp /= 2;
    q.insert(tmp);
  }
  cout << *q.begin();
}
int main() {
  int t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
