#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<int> vec(N);
  for (int i = 0; i < N; i++) {
    cin >> vec.at(i);
  }
  int ooki;
  for (int i = 0; i < N; ++i) {
    for (int j = i + 1; j < N; ++j) {
      if (vec.at(i) > vec.at(j)) {
        ooki = vec.at(i);
        vec.at(i) = vec.at(j);
        vec.at(j) = ooki;
      }
    }
  }
  double goke = 0;
  for (int i = 0; i < N; i++) {
    if (i = 0) {
      goke = (vec.at(0) + vec.at(1)) / 2.00;
    } else {
      goke = (goke + vec.at(i + 1)) / 2.00;
    }
  }
  cout << goke << endl;
}
