#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int v[n];
  for (int i = 0; i < n; i++) cin >> v[i];
  sort(v, v + n);
  double temp = 0;
  for (int i = 0; i < n - 1; i++) {
    temp = (double)(v[i] + v[i + 1]) / 2;
    v[i + 1] = temp;
  }
  cout << temp;
}
