#include <bits/stdc++.h>
using namespace std;
int main(int argc, char const *argv[]) {
  int N;
  cin >> N;
  vector<float> v;
  float a;
  for (int i = 0; i < N; i++) {
    cin >> a;
    v.push_back(a);
  }
  sort(v.begin(), v.end());
  float V = v[0];
  for (int i = 1; i < N - 1; i++) {
    V = (V + v[i]) / 2;
  }
  cout << V << endl;
  return 0;
}
