#include <bits/stdc++.h>
using namespace std;
int main() {
  double v[50];
  int n;
  cin >> n;
  double a;
  for (int i = 0; i < n; i++) {
    cin >> a;
    v[i] = a;
  }
  for (int i = 0; i < n - 1; i++) {
    for (int j = i + 1; j < n; j++) {
      if (v[j - 1] < v[j]) {
        int temp = v[j];
        v[j] = v[j - 1];
        v[j - 1] = temp;
      }
    }
  }
  for (int i = n - 2; i >= 0; i--) {
    v[i] = (v[i] + v[i + 1]) / 2;
  }
  printf("%0.10f", v[0]);
}
