#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  vector<int> x;
  cin >> n;
  for (int i = 0; i < n; i++) {
    int temp;
    cin >> temp;
    x.push_back(temp);
  }
  sort(x.begin(), x.end());
  float val = (x[0] + x[1]) / 2.0f;
  x.erase(x.begin(), x.begin() + 1);
  while (x.size() == 0) {
    sort(x.begin(), x.end());
    val = (val + x[0]) / 2.0f;
    x.erase(x.begin());
  }
  cout << val << endl;
  return 0;
}
