#include <bits/stdc++.h>
using namespace std;
using namespace std;
void solve() {
  long long n;
  cin >> n;
  set<double> s;
  for (long long i = 0; i < n; i++) {
    double d;
    cin >> d;
    s.insert(d);
  }
  while (s.size() > 1) {
    set<double>::iterator p = s.begin();
    double x = *(p);
    p++;
    double y = *(p);
    p--;
    s.erase(p);
    set<double>::iterator pr = s.begin();
    s.erase(pr);
    double z = (double)(((double)(x) + (double)(y)) / (double)2);
    s.insert(z);
  }
  set<double>::iterator p = s.begin();
  printf("%.8lf\n", *p);
}
int main() {
  ios::sync_with_stdio(true);
  cin.tie(0);
  cout.tie(0);
  long long t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
