#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, p;
  cin >> n;
  vector<long long> v;
  for (long long i = 0; i < n; i++) {
    cin >> p;
    v.push_back(p);
  }
  sort(v.begin(), v.end());
  double dd = (v[0] + v[1]) / 2;
  for (long long i = 2; i < n; i++) {
    dd += v[i];
    dd /= 2;
  }
  cout << dd;
}
