#include <bits/stdc++.h>
using namespace std;
long long int poww(long long int a, long long int b) {
  long long int ans = 1;
  for (int i = 1; i <= b; i++) {
    ans *= a;
  }
  return ans;
}
int max(int a, int b, int c) {
  if (a >= b && a >= c) return a;
  if (b >= a && b >= c) return b;
  return c;
}
int main() {
  cout << fixed << setprecision(6);
  string s;
  int n;
  cin >> n;
  vector<double> a;
  for (int(i) = 0; i < (n); (i)++) {
    int t;
    cin >> t;
    a.push_back(t);
  }
  sort((a).begin(), (a).end());
  int i = 0;
  while (n > 1) {
    int j = 0;
    int k = 0;
    while (true) {
      if (j >= n - 1) break;
      a[k] = (a[j] + a[j + 1]) / 2;
      j += 2;
      k++;
    }
    if (n % 2 == 1) {
      a[k++] = a[j];
    }
    n = k;
    i++;
  }
  cout << a[0];
}
