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