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