#include <bits/stdc++.h>
using namespace std;
template <class T>
ostream &operator<<(ostream &out, vector<T> const &v) {
  for (auto &&a : v) out << a << " ";
  out << endl;
  return out;
}
template <class T>
void dump(T &a) {
  cout << a << endl;
}
void solve();
int main() {
  solve();
  return 0;
}
void solve() {
  cout.precision(15);
  cout << fixed;
  int n;
  cin >> n;
  multiset<double> S;
  for (int i = 0; i < n; i++) {
    double d;
    cin >> d;
    S.insert(d);
  }
  while (S.size() > 1) {
    double min_ = 100000.0;
    double a, b;
    for (auto it = S.begin(); it != S.end(); it++) {
      auto jt = it;
      jt++;
      for (; jt != S.end(); jt++) {
        if (min_ > fabs(*jt - *it)) {
          min_ = fabs(*jt - *it);
          a = *it;
          b = *jt;
        }
      }
    }
    S.erase(a);
    S.erase(b);
    S.insert((a + b) / 2);
  }
  cout << *S.begin() << endl;
}
