#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  priority_queue<long double, vector<long double>, greater<long double> > vNum;
  for (int i = 0; i < N; ++i) {
    long double tmp = 0;
    cin >> tmp;
    vNum.push(tmp);
  }
  while (true) {
    if (vNum.size() == 1) {
      break;
    }
    int AA = vNum.top();
    vNum.pop();
    int BB = vNum.top();
    vNum.pop();
    vNum.push((AA + BB) / 2.0f);
  }
  printf("%.6f", vNum.top());
}
