#include <bits/stdc++.h>
using namespace std;
const bool DEBUG = false;
int main(int argc, char const *argv[]) {
  int N;
  cin >> N;
  double tmp;
  set<double> v;
  for (size_t i = 0; i < N; i++) {
    cin >> tmp;
    v.insert(tmp);
  }
  double lhs, rhs, result;
  while (v.size() > 1) {
    auto itr = v.begin();
    lhs = *itr;
    itr = v.erase(itr);
    rhs = *itr;
    v.erase(itr);
    result = (lhs + rhs) / 2;
    v.insert(result);
  }
  cout << *(v.begin()) << endl;
  return 0;
}
