#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int i, n;
  double ans = 0;
  cin >> n;
  int v[n];
  for (i = 0; i < n; i++) cin >> v[i];
  sort(v, v + n);
  ans = (v[0] + v[1]) / 2;
  for (i = 2; i < n; i++) {
    ans = (ans + v[i]) / 2;
  }
  cout << fixed << setprecision(5) << ans << endl;
}
