#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  int V[100];
  double ans = 0;
  cin >> N;
  for (int i = 0; i < N; i++) {
    cin >> V[i];
  }
  sort(V, V + N);
  double temp;
  for (int i = 0; i < N - 1; i++) {
    temp = double(V[i] + V[i + 1]) / 2;
    V[i + 1] = temp;
    V[i] = -1;
    sort(V, V + N);
  }
  cout << temp << endl;
}
