#include <bits/stdc++.h>
using namespace std;
int main() {
  int N, i = 0, t;
  cin >> N;
  double v[N];
  for (i = 0; i < N; i++) {
    cin >> t;
    v[i] = t;
  }
  sort(v, v + N);
  double temp = (v[0] + v[1]) / 2.0;
  if (N > 2) {
    for (i = 2; i < N; i++) {
      temp = (temp + v[2]) / 2.0;
    }
  }
  cout << temp << endl;
}
