#include <bits/stdc++.h>
using namespace std;
const int MOD = 1000000007;
struct mint {
  int n;
  mint(int n_ = 0) : n(n_) {}
};
mint operator-(mint a) { return -a.n + MOD * (a.n != 0); }
mint operator+(mint a, mint b) {
  int x = a.n + b.n;
  return x - (x >= MOD) * MOD;
}
mint operator-(mint a, mint b) {
  int x = a.n - b.n;
  return x + (x < 0) * MOD;
}
mint operator*(mint a, mint b) { return (long long)a.n * b.n % MOD; }
mint &operator+=(mint &a, mint b) { return a = a + b; }
mint &operator-=(mint &a, mint b) { return a = a - b; }
mint &operator*=(mint &a, mint b) { return a = a * b; }
istream &operator>>(istream &i, mint &a) { return i >> a.n; }
ostream &operator<<(ostream &o, mint a) { return o << a.n; }
vector<mint> F_{1, 1}, R_{1, 1}, I_{0, 1};
void check_fact(int n) {
  for (int i = I_.size(); i <= n; i++) {
    I_.push_back(I_[MOD % i] * (MOD - MOD / i));
    F_.push_back(F_[i - 1] * i);
    R_.push_back(R_[i - 1] * I_[i]);
  }
}
mint I(int n) {
  check_fact(abs(n));
  return n >= 0 ? I_[n] : -I_[n];
}
mint F(int n) {
  check_fact(n);
  return n < 0 ? 0 : F_[n];
}
mint R(int n) {
  check_fact(n);
  return n < 0 ? 0 : R_[n];
}
mint C(int n, int r) { return F(n) * R(n - r) * R(r); }
mint P(int n, int r) { return F(n) * R(n - r); }
mint H(int n, int r) { return n == 0 ? (r == 0) : C(n + r - 1, r); }
template <class T>
inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
vector<T> enum_div(T n) {
  vector<T> ret;
  for (T i = 1; i * i <= n; i++) {
    if (n % i == 0) {
      ret.push_back(i);
      if (i * i != n) ret.push_back(n / i);
    }
  }
  return ret;
}
template <typename T>
T gcd(T x, T y) {
  if (y == 0)
    return x;
  else
    return gcd(y, x % y);
}
template <typename T>
T lcm(T x, T y) {
  return (x / gcd(x, y)) * y;
}
int N;
int v[50];
int main(void) {
  cin >> N;
  for (int i = 0; i < (N); i++) cin >> v[i];
  sort(v, v + N);
  float s;
  s = (v[0] + v[1]) / 2.0;
  for (int i = 2; i < N; i++) {
    s = (s + v[2]) / 2.0;
  }
  printf("%.6f", s);
  return 0;
}
