#include <bits/stdc++.h>
using namespace std;
const long long INF = 1 << 29;
int main() {
  int n;
  cin >> n;
  double v[n];
  for (int i = 0; i < (int)(n); i++) {
    cin >> v[i];
  }
  sort(v, v + n);
  double ave = 0.0;
  ave = (v[0] + v[1]) / 2;
  for (int i = 2; i < n; i++) {
    ave = (v[i] + ave) / 2;
  }
  cout << setprecision(3) << ave << endl;
}
