#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, v, a, b;
  double c;
  cin >> n;
  std::priority_queue<int, std::vector<int>, std::greater<int> > que;
  for (int i = 0; i < (int)(n); i++) {
    cin >> v;
    que.push(v);
  }
  while (!que.empty()) {
    a = que.top();
    que.pop();
    b = que.top();
    que.pop();
    c = (a + b) / (double)2;
    if (!que.empty()) {
      que.push(c);
    }
  }
  cout << c;
  return 0;
}
