#include <bits/stdc++.h>
using namespace std;
signed main() {
  long long n;
  cin >> n;
  vector<double> v(n);
  for (long long i = 0; i < n; i++) {
    cin >> v[i];
  }
  sort(v.begin(), v.end());
  while (v.size() > 1) {
    double x = (double)(v[0] + (double)v[1]) / 2;
    v.erase(v.begin());
    v.erase(v.begin());
    v.push_back(x);
  }
  cout << v[0] << endl;
  return 0;
}
