#include <bits/stdc++.h>
using namespace std;
int countDivisors(int n) {
  int cnt = 0;
  for (int i = 1; i <= sqrt(n); i++) {
    if (n % i == 0) {
      if (n / i == i)
        cnt++;
      else
        cnt = cnt + 2;
    }
  }
  return cnt;
}
int power(int x, unsigned int y) {
  int temp;
  if (y == 0) return 1;
  temp = power(x, y / 2);
  if (y % 2 == 0)
    return temp * temp;
  else
    return x * temp * temp;
}
int main() {
  long long n, s = 0, c = 1;
  float sum = 0.0f, ans;
  cin >> n;
  long long a[n];
  for (long long i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a, a + n);
  for (long long i = 2; i < n; i++) {
    s += a[i] * power(2, c);
    c++;
  }
  s = s + a[0] + a[1];
  cout << (float)s / power(2, n - 1);
}
