#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  float a;
  vector<float> v;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a;
    v.push_back(a);
  }
  sort(v.begin(), v.end());
  for (int i = 0; i < v.size(); i++) {
    if (i == 0) {
      a = (v[0] + v[1]) / 2;
    } else if (i > 1) {
      a = (a + v[i]) / 2;
    }
  }
  cout << a << endl;
  return 0;
}
