#include <bits/stdc++.h>
using namespace std;
int main() {
  unsigned long long n;
  float ans;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  sort(v.begin(), v.end());
  stack<float> a;
  for (int i = n - 1; i >= 0; i--) {
    a.push(v[i]);
  }
  while (a.size() != 1) {
    float p = a.top();
    a.pop();
    float q = a.top();
    a.pop();
    ans = (p + q) / 2;
    a.push(ans);
  }
  cout << a.top();
  return 0;
}
