#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  float v;
  priority_queue<int, vector<int>, greater<int> > que;
  float res = 0;
  cin >> N;
  for (int i = 0; i < N; i++) {
    cin >> v;
    que.push(v);
  }
  while (que.size() != 1) {
    float a, b;
    a = que.top();
    que.pop();
    b = que.top();
    que.pop();
    res = (a + b) / 2;
    que.push(res);
  }
  cout << res << endl;
  return 0;
}
