#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  sort(v.begin(), v.end());
  int sz = v.size();
  while (sz > 0) {
    if (sz % 2 == 0) {
      for (int i = 0; i < sz - 1; i += 2) {
        v[i / 2] = (v[i] + v[i + 1]) / 2;
      }
    } else {
      for (int i = 0; i < sz - 2; i += 2) {
        v[i / 2] = (v[i] + v[i + 1]) / 2;
        v[sz / 2] = v.back();
      }
    }
    if (sz == 2) {
      cout << v.front() << endl;
      return 0;
    }
    sz /= 2;
    if (sz == 1) {
      cout << (v[0] + v[1]) / 2 << endl;
      return 0;
    } else {
      if (sz % 2 == 0) {
        v.resize(sz);
      } else if (sz % 2 != 0) {
        v.resize(sz + 1);
      }
    }
  }
  return 0;
}
