#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<double> vv;
  int n;
  cin >> n;
  while (n--) {
    int x;
    cin >> x;
    vv.push_back(x);
  }
  while (vv.size() != 1) {
    int p1, p2;
    double ab = 1001;
    for (int i = 0; i < vv.size(); ++i) {
      for (int j = 0; j < vv.size(); ++j) {
        if (i == j) continue;
        if (abs(vv[i] - vv[j]) < ab) {
          ab = abs(vv[i] - vv[j]);
          p1 = i;
          p2 = j;
        }
      }
    }
    double v = (vv[p1] + vv[p2]) / 2;
    vv[p1] = v;
    vv.erase(vv.begin() + p2);
  }
  cout << vv[0] << endl;
}
