#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
const int MOD = 1000000007;
int main() {
  int n;
  cin >> n;
  set<double> a;
  double v;
  for (int i = (0); i < (n); i++) {
    cin >> v;
    a.insert(v);
  }
  while (a.size() > 1) {
    auto fi = a.begin();
    auto se = fi;
    se++;
    double c = (*fi + *se) / 2;
    a.erase(fi);
    a.erase(se);
    a.insert(c);
  }
  cout << fixed << setprecision(10) << *(a.begin()) << endl;
}
