#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  long double x, y, sum = 0.0;
  cin >> n;
  vector<long long> a;
  vector<long double> b;
  for (long long i = long long(0); i <= long long(n - 1); i++) cin >> a[i];
  if (n == 2) {
    cout << (double(a[1] + a[2]) / 2);
    return 0;
  }
  sort(a.begin(), a.end());
  x = (a[0] + a[1]) / 2;
  for (long long i = long long(2); i <= long long(n - 1); i++)
    x = (x + a[i]) / 2;
  cout << x;
}
