#include <bits/stdc++.h>
using namespace std;
const int mod = 1000000007;
const int inf = (int)1e9 + 7;
const long long INF = 1LL << 60;
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
long long GCD(long long a, long long b) { return b ? GCD(b, a % b) : a; }
int round_int(int a, int b) { return (a + (b - 1)) / b; }
int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
constexpr auto MAX = 100010;
int main() {
  int n;
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < n; i++) cin >> v[i];
  double tmp = 0;
  for (int i = 0; i < n - 1; ++i) {
    sort(v.begin(), v.end());
    vector<pair<int, int>> pairs(v.size() - 1);
    for (int j = 0; j < v.size() - 1; j++)
      pairs[j] = make_pair(v[j + 1] - v[j], j);
    sort(pairs.begin(), pairs.end());
    tmp = (v[pairs[0].second + 1] + v[pairs[0].second]) / 2;
    v.erase(v.begin() + pairs[0].second + 1);
    v.erase(v.begin() + pairs[0].second);
    v.push_back(tmp);
  }
  cout << setprecision(10) << v[0] << endl;
}
