#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pint = pair<int, int>;
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() / 2; ++i) {
    double add = (inArr[i * 2] + inArr[i * 2 + 1]) / 2.0;
    result.push_back(add);
  }
  if (inArr.size() % 2 != 0) {
    result.push_back(inArr[inArr.size() - 1]);
  }
  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.begin(), v.end());
  double ans = 0.0;
  value(v, ans);
  cout << fixed << setprecision(14) << ans << endl;
  return 0;
}
