#include <bits/stdc++.h>
using namespace std;
long long a, b, c, m, n, ans;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < (n); i++) cin >> v[i];
  sort(v.begin(), v.end());
  int i = 0;
  int j = n - 1;
  while (!(i == j)) {
    double first = v[i + 1] - v[i];
    double second = v[j] - v[j - 1];
    if (first < second) {
      v[i + 1] = (v[i + 1] + v[i]) / 2;
      i++;
    } else {
      v[j - 1] = (v[j] + v[j - 1]) / 2;
      j--;
    }
  }
  cout << v[i] << endl;
  return 0;
}
