#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<ll, ll>;
const ll MOD = 1e9 + 7, N = 50 + 10;
ll a[N], sum[N];
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  ll n;
  cin >> n;
  set<ld> s;
  for (ll i = 0; i < n; i++) {
    ll x;
    cin >> x;
    s.insert(x);
  }
  while (s.size() != 1) {
    ld x = *s.begin();
    s.erase(s.begin());
    ld y = *s.begin();
    s.erase(s.begin());
    s.insert((x + y) / 2);
  }
  cout << *s.begin() << '\n';
  return 0;
}
