#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int v[n];
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  if (n == 1) {
    cout << v[0];
    return 0;
  }
  sort(v, v + n);
  float avg = 0;
  avg = (float)(v[n - 1] + v[n - 2]) / 2;
  for (int i = (n - 3); i >= 0; i--) {
    avg = (avg + v[i]) / 2;
  }
  cout << avg;
  return 0;
}
