#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pint = pair<int, int>;
void swap(double& a, double& b) {
  double tmp = a;
  a = b;
  b = tmp;
}
void sort(vector<double>& arr, int l, int r) {
  if (r - l < 1) {
    return;
  }
  double pivot = arr[r];
  int i = l;
  for (int j = l; j < r; ++j) {
    if (arr[j] < pivot) {
      swap(arr[i], arr[j]);
      i++;
    }
  }
  swap(arr[i], arr[r]);
  sort(arr, l, i - 1);
  sort(arr, i + 1, r);
}
void value(vector<double>& inArr, double& out) {
  if (inArr.size() == 1) {
    out = inArr[0];
    return;
  }
  vector<double> result;
  for (int i = 0; i < inArr.size(); i += 2) {
    double add = 0;
    if (i + 1 < inArr.size()) {
      add = (inArr[i] + inArr[i + 1]) / 2.0;
    } else {
      add = inArr[i];
    }
    result.push_back(add);
  }
  value(result, out);
}
int main() {
  int N;
  cin >> N;
  vector<double> v(N);
  for (int i = 0; i < N; ++i) {
    cin >> v[i];
  }
  sort(v, 0, N - 1);
  double ans = 0.0;
  value(v, ans);
  cout << ans << endl;
  return 0;
}
