#include <bits/stdc++.h>
using namespace std;
float getave(float a, float b) {
  float ave;
  ave = (a + b) / 2;
  return ave;
}
int main() {
  int n;
  cin >> n;
  vector<float> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v.at(i);
  }
  sort(v.begin(), v.end());
  for (int i = 0; i < n; i++) {
    v.at(i + 1) = getave(v.at(i), v.at(i + 1));
  }
  cout << v.at(n - 1) << endl;
}
