#include <bits/stdc++.h>
using ll = long long;
using ld = long double;
using namespace std;
const int INF = 1e9 + 100;
const ll INF64 = 7e18l;
const int mod = 1000000007;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = (0); i < (n); i++) cin >> v[i];
  std::priority_queue<int, std::vector<int>, std::greater<int> > que;
  for (int i = (0); i < (n); i++) que.push(v[i]);
  for (int i = 1; i <= n - 1; i++) {
    double first = que.top();
    que.pop();
    double second = que.top();
    que.pop();
    que.push((first + second) / 2);
  }
  long double ans = que.top();
  cout << ans << endl;
  return 0;
}
