#include <bits/stdc++.h>
#pragma warning(disable : 4996)
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("-ffloat-store")
using namespace std;
bool isPrime(unsigned long long int n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;
  for (unsigned long long int i = 5; i * i <= n; i = i + 6)
    if (n % i == 0 || n % (i + 2) == 0) return false;
  return true;
}
void solve() {
  int n;
  cin >> n;
  long long int sum = 0;
  long long int mul = 1;
  vector<float> v;
  for (int i = 0; i < n; i++) {
    int input;
    cin >> input;
    v.push_back(input);
  }
  sort((v).begin(), (v).end());
  while (v.size() > 2) {
    long long int a = v[0], b = v[1];
    v.erase(v.begin());
    v.erase(v.begin());
    v.push_back((float)(a + b) / 2);
    sort((v).begin(), (v).end());
  }
  cout << (float)(v[0] + v[1]) / 2 << endl;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long int t = 1;
  while (t--) {
    solve();
  }
}
