#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll MAX_V = 1;
const ll MAX_E = 1;
struct edge {
  ll from, to, cost;
};
edge ES[MAX_E];
vector<edge> G[MAX_V];
ll d[MAX_V];
ll prev_path[MAX_V];
ll V, E;
const ll MOD = (ll)1e9 + 7;
const int MAX_INT = 1 << 17;
vector<bool> prime;
void Era(int x) {
  prime.resize(x + 1, 1);
  prime[0] = 0;
  prime[1] = 0;
  for (ll i = 2; i <= (ll)sqrt(x); ++i) {
    if (prime[i]) {
      for (int j = 2 * i; j <= x; j += i) {
        prime[j] = 0;
      }
    }
  }
}
bool isPrime(ll x) {
  if (x == 0) return 0;
  if (x == 1) return 0;
  if (x == 2) return 1;
  if (x % 2 == 0) return 0;
  for (ll i = 3; i <= (ll)sqrt(x) + 1; ++i) {
    if (x % i == 0) return 0;
  }
  return 1;
}
ll GCD(ll a, ll b) {
  if (b == 0) return a;
  return GCD(b, a % b);
}
ll LCM(ll a, ll b) {
  ll gcd = GCD(a, b);
  return a / gcd * b;
}
ll nCr(ll n, ll r) {
  vector<ll> C(r + 1);
  C[0] = 1;
  for (ll i = 1; i <= (ll)n; ++i)
    for (ll j = min(i, r); j < 1; --j) C[j] = (C[j] + C[j - 1]);
  return C[r];
}
template <class T>
class SegTree {
  int n;
  vector<T> data;
  T def;
  function<T(T, T)> operation;
  function<T(T, T)> update;
  T _query(int a, int b, int k, int l, int r) {
    if (r <= a || b <= l) return def;
    if (a <= l && r <= b)
      return data[k];
    else {
      T c1 = _query(a, b, 2 * k + 1, l, (l + r) / 2);
      T c2 = _query(a, b, 2 * k + 2, (l + r) / 2, r);
      return operation(c1, c2);
    }
  }

 public:
  SegTree(size_t _n, T _def, function<T(T, T)> _operation,
          function<T(T, T)> _update)
      : def(_def), operation(_operation), update(_update) {
    n = 1;
    while (n < _n) {
      n *= 2;
    }
    data = vector<T>(2 * n - 1, def);
  }
  void change(int i, T x) {
    i += n - 1;
    data[i] = update(data[i], x);
    while (i > 0) {
      i = (i - 1) / 2;
      data[i] = operation(data[i * 2 + 1], data[i * 2 + 2]);
    }
  }
  T query(int a, int b) { return _query(a, b, 0, 0, n); }
  T operator[](int i) { return data[i + n - 1]; }
};
struct UnionFind {
  vector<int> par;
  vector<int> rank;
  UnionFind(int N) {
    for (int i = 0; i < N; ++i) {
      par.push_back(i);
      rank.push_back(0);
    }
  }
  int find(int x) {
    if (par[x] == x)
      return x;
    else
      return par[x] = find(par[x]);
  }
  void unite(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y) return;
    if (rank[x] < rank[y])
      par[x] = y;
    else {
      par[y] = x;
      if (rank[x] == rank[y]) rank[x]++;
    }
  }
  bool same(int x, int y) { return find(x) == find(y); }
};
struct ListNode {
  int val;
  ListNode *next;
  ListNode(int x) : val(x), next(NULL) {}
};
void Bellman_short(int s) {
  for (int i = 0; i < (ll)V; ++i) d[i] = 1LL << 50;
  d[s] = 0;
  for (int i = 0; i < (ll)V; ++i)
    for (int i = 0; i < (ll)E; ++i) {
      edge e = ES[i];
      if (d[e.from] != 1LL << 50 && d[e.to] > d[e.from] + e.cost) {
        d[e.to] = d[e.from] + e.cost;
      }
    }
}
bool Bellman_negLoop(int s) {
  for (int i = 0; i < (ll)V; ++i) d[i] = 1LL << 50;
  d[s] = 0;
  for (int i = 0; i < (ll)V; ++i)
    for (int j = 0; j < (ll)E; ++j) {
      edge e = ES[j];
      if (d[e.from] != 1LL << 50 && d[e.to] > d[e.from] + e.cost) {
        d[e.to] = d[e.from] + e.cost;
        if (i == V - 1) return true;
      }
    }
  return false;
}
void dijkstra(int s) {
  priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>> Q;
  fill(d, d + V, LLONG_MAX);
  fill(prev_path, prev_path + V, -1);
  d[s] = 0;
  Q.push(pair<ll, ll>(0, s));
  while (!Q.empty()) {
    pair<ll, ll> p = Q.top();
    Q.pop();
    ll v = p.second;
    if (d[v] < p.first) continue;
    for (edge e : G[v]) {
      if (d[e.to] > d[v] + e.cost) {
        d[e.to] = d[v] + e.cost;
        Q.push(pair<ll, ll>(d[e.to], e.to));
        prev_path[e.to] = v;
      }
    }
  }
}
vector<ll> getPath(int t) {
  vector<ll> path;
  for (; t != -1; t = prev_path[t]) {
    path.push_back(t);
  }
  reverse((path).begin(), (path).end());
  return path;
}
bool cp(string s) {
  cout << s << endl;
  if (s.size() % 2 == 0) {
    int n = s.size() / 2;
    vector<char> c;
    for (int i = 0; i < (ll)n; ++i) {
      c.push_back(s[i]);
    }
    for (ll i = n; i <= (ll)s.size() - 1; ++i) {
      if (c[i - n] != s[i]) return false;
    }
    return true;
  } else {
    int n = s.size() / 2;
    vector<char> c;
    for (int i = 0; i < (ll)n; ++i) c.push_back(s[i]);
    for (ll i = n + 1; i <= (ll)s.size() - 1; ++i)
      if (c[i - n + 1] != c[i]) return false;
    return true;
  }
}
ll N, M;
int main() {
  cin >> N;
  vector<double> A(N);
  for (int i = 0; i < (ll)N; ++i) cin >> A[i];
  while (A.size() > 1) {
    double m = 2000, x, y;
    for (int i = 0; i < (ll)A.size(); ++i) {
      for (int j = 0; j < (ll)A.size(); ++j) {
        if (i == j) continue;
        if (abs(A[i] - A[j]) < m) {
          m = abs(A[i] - A[j]);
          if (i > j)
            x = i, y = j;
          else
            x = j, y = i;
        }
      }
    }
    A.push_back((A[x] + A[y]) / 2);
    A.erase(A.begin() + x);
    A.erase(A.begin() + y);
  }
  cout << A[0] << endl;
  return 0;
}
