#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<float> v(n);
  for (int i = 0; i < n; i++) cin >> v[i];
  for (int i = 0; i < n - 1; i++) {
    float a = *min_element(v.begin(), v.end());
    v.erase(min_element(v.begin(), v.end()));
    float b = *min_element(v.begin(), v.end());
    v.erase(min_element(v.begin(), v.end()));
    v.push_back((float)(a + b) / 2);
  }
  cout << v.front() << endl;
  return 0;
}
