#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
long long dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
long long gcd(long long x, long long y) {
  long long r;
  while ((r = x % y) != 0) {
    x = y;
    y = r;
  }
  return y;
}
long long lcm(long long a, long long b) {
  long long g = gcd(a, b);
  return a / g * b;
}
long long digsum(long long n) {
  long long sum = 0;
  while (n > 0) {
    sum += n % 10;
    n /= 10;
  }
  return sum;
}
int main() {
  long long n;
  cin >> n;
  vector<double> a(n);
  for (int i = 0; i < n; i++) cin >> a[i];
  sort((a).rbegin(), (a).rend());
  while ((int)a.size() > 1) {
    for (long long i = (int)a.size() - 1; i > 0; i -= 2) {
      a[i - 1] = (a[i] + a[i - 1]) / 2;
      a.pop_back();
    }
  }
  printf("%.10f\n", a[0]);
  return 0;
}
