#include <bits/stdc++.h>
using namespace std;
int N;
float v[51];
int main() {
  cin >> N;
  for (int i = 0; i < N; i++) {
    cin >> v[i];
  }
  sort(v, v + N);
  float sum = 0;
  long long div = 2;
  for (int i = N - 1; i > 0; i--) {
    sum += v[i] / div;
    div *= 2;
  }
  sum += v[0] / (div / 2);
  cout << sum << endl;
  return 0;
}
