#include <bits/stdc++.h>
using namespace std;
using ll = long long;
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());
  int sum = 0;
  for (int i = 0; i < (int)(n); i++) {
    if (i == 0)
      sum += v[0];
    else
      sum += v[i] * pow(2, i - 1);
  }
  printf("%.10f", (double)(sum) / (double)(pow(2, n - 1)));
}
