#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const long long MOD = 1000000007;
long long dp[100005][13];
void Main() {
  int n;
  cin >> n;
  priority_queue<double> V;
  for (int i = 0; i < n; ++i) {
    int v;
    cin >> v;
    V.push(-v);
  }
  while (V.size() != 1) {
    int a = V.top();
    V.pop();
    int b = V.top();
    V.pop();
    V.push((a + b) / 2.0);
  }
  cout << abs(V.top()) << endl;
}
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
  Main();
}
