#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  long long int n;
  cin >> n;
  priority_queue<float> q;
  for (int i = 0; i < n; i++) {
    int temp;
    cin >> temp;
    q.push(-temp);
  }
  float temp;
  while (--n) {
    int a = -q.top();
    q.pop();
    int b = -q.top();
    q.pop();
    temp = float((a + b) / 2);
    q.push(-temp);
  }
  cout << temp << "\n";
  return 0;
}
