#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, cnt = 1;
  int v[50];
  double ans = 0.0;
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> v[i];
  }
  sort(v, v + n);
  for (i = n - 1; i >= 0; i--) {
    if (i != 0) {
      cnt *= 2;
    }
    ans += (double)v[i] / cnt;
  }
  cout << ans << endl;
}
