#include <bits/stdc++.h>
using namespace std;
int main(void) {
  double n = 0;
  double a[110000], b = 0;
  cin >> n;
  cin >> a[0];
  b += a[0];
  for (int i = 1; i < n; i++) {
    cin >> a[i];
    b = (b + a[i]) / 2;
  }
  cout << b << endl;
}
