#include <bits/stdc++.h>
using namespace std;
bool prime[200005];
void sieve() {
  memset(prime, true, sizeof(prime));
  for (long long p = 2; p * p < 200005; p++) {
    if (prime[p] == true) {
      for (long long i = p * p; i < 200005; i += p) prime[i] = false;
    }
  }
}
long long powmod(long long x, long long y, long long mod) {
  long long res = 1;
  x = x % mod;
  while (y > 0) {
    if (y & 1) {
      res = (res * x) % mod;
    }
    y = y >> 1;
    x = (x * x) % mod;
  }
  return res;
}
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n;
  cin >> n;
  long long a[n];
  priority_queue<long double, vector<long double>, greater<long double> > pq;
  for (long long i = 0; i < n; i++) {
    cin >> a[i];
    pq.push((long double)a[i]);
  }
  while (pq.size() > 1) {
    long long x = pq.top();
    pq.pop();
    long long y = pq.top();
    pq.pop();
    pq.push((x + y) / 2.0);
  }
  cout << setprecision(10);
  cout << pq.top() << endl;
  return 0;
}
