#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
const int MAX = 10000000;
template <typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T>
T gcd(T a, T b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
int main() {
  int n;
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < (int)(n); i++) cin >> v[i];
  sort(v.begin(), v.end());
  double max = 0;
  do {
    double z = (v[0] + v[1]) / 2.0;
    for (int i = (2); i < (int)(n); i++) {
      z = (z + v[i]) / 2.0;
    }
    chmax(max, z);
  } while (next_permutation(v.begin(), v.end()));
  printf("%.10f", max);
  return 0;
}
