#include <bits/stdc++.h>
using namespace std;
using P = pair<int, int>;
int main() {
  int n;
  double temp;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < (n); ++i) cin >> v.at(i);
  sort(v.begin(), v.end());
  for (int k = 0; k < (n - 1); ++k) {
    temp = (double)(v[0] + v[1]) / (double)2;
    v.erase(v.begin());
    v.erase(v.begin());
    for (int i = 0; i < (v.size()); ++i) {
      if (v[i] >= temp) {
        v.insert(v.begin() + i, temp);
        break;
      }
    }
  }
  printf("%.10f\n", temp);
}
