#include <bits/stdc++.h>
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
const long long mod = 1e9 + 7;
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n;
  cin >> n;
  deque<double> f;
  for (long long x = 0; x < n; x++) {
    long long t;
    cin >> t;
    if (t & 1)
      f.push_back(t);
    else
      f.push_front(t);
  }
  while (f.size() != 1) {
    double fi = f.front();
    f.pop_front();
    double se = f.front();
    f.pop_front();
    double _1 = (fi + se) / (double)2;
    if ((long long)_1 == (double)_1) {
      if ((long long)_1 % 2 == 0)
        f.push_front(_1);
      else
        f.push_back(_1);
    } else
      f.push_back(_1);
  }
  double ans = f.front();
  cout << ans << '\n';
  return 0;
}
