#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<float> v(N);
  for (int i = 0; i < N; i++) {
    cin >> v[i];
  }
  sort(v.begin(), v.end());
  while (v.size() != 1) {
    int num = 0;
    sort(v.begin(), v.end());
    float m = v[1] - v[0];
    for (int i = 1; i < v.size() - 1; i++) {
      if ((v[i + 1] - v[i]) < m) {
        num = i;
      }
    }
    v[num] = (v[num] + v[num + 1]) / 2;
    v.erase(v.begin() + num + 1);
  }
  cout << setprecision(9) << v[0] << endl;
}
