#include <bits/stdc++.h>
using namespace std;
long long power(long long, long long);
long long mpower(long long, long long);
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n;
  cin >> n;
  multiset<double> s;
  for (long long i = 0; i < n; i++) {
    long long t;
    cin >> t;
    s.insert(t);
  }
  for (long long i = 0; i < n - 1; i++) {
    double x = *s.begin();
    s.erase(s.begin());
    double y = *s.begin();
    s.erase(s.begin());
    s.insert((x + y) / 2);
  }
  cout << fixed << setprecision(10);
  cout << *s.begin();
  return 0;
}
long long power(long long a, long long b) {
  long long res = 1;
  while (b > 0) {
    if (b % 2 == 1) res = res * a;
    a = a * a;
    b = b / 2;
  }
  return res;
}
long long mpower(long long a, long long b) {
  long long res = 1;
  while (b > 0) {
    if (b % 2 == 1) {
      res = (res * a) % 1000000007;
    }
    a = (a * a) % 1000000007;
    b = b / 2;
  }
  return res;
}
