#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  int a;
  double sum;
  double gu;
  cin >> N;
  for (int i = 0; i < N; i++) {
    cin >> a;
    if (i == 0) {
      gu = a;
    } else {
      gu = (a + gu) / 2.0;
    }
  }
  cout << gu << endl;
}
