#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const long long oo = 1e9 + 10;
const int Max = 1e6 + 10;
long long powmod(long long a, long long b) {
  long long res = 1;
  a %= mod;
  assert(b >= 0);
  for (; b; b >>= 1) {
    if (b & 1) res = res * a % mod;
    a = a * a % mod;
  }
  return res;
}
long long n, a, b;
void solve() {
  priority_queue<double> q;
  cin >> n;
  double t;
  for (int i = 0; i < n; i++) {
    cin >> t;
    q.push(t);
  }
  while (q.size() > 1) {
    double x = q.top();
    q.pop();
    double y = q.top();
    q.pop();
    q.push((x + y) / 2);
  }
  cout << q.top();
}
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  solve();
  return 0;
}
