#include <bits/stdc++.h>
using namespace std;
int const N = 1e5 + 1;
int n, v[N];
int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; ++i) scanf("%d", v + i);
  sort(v, v + n);
  queue<double> q;
  for (int i = 0; i < n; ++i) q.push(v[i]);
  vector<int> vec;
  while (!q.empty()) {
    double x = q.front();
    q.pop();
    if (!q.size()) {
      cout << x;
      break;
    }
    double y = q.front();
    q.pop();
    q.push((x + y) / 2.0);
  }
}
