#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
int main() {
  int n;
  cin >> n;
  int v[n];
  for (int i = 0; i < (int)(n); i++) cin >> v[i];
  sort(v, v + n);
  ld ans = (v[0] + v[1]) / 2;
  for (int i = 2; i < n; i++) {
    ans = (long double)((ans + v[i]) / 2);
  }
  cout << fixed;
  cout << setprecision(20);
  cout << ans << endl;
}
