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