#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double v[55];
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  for (int i = 0; i < n; i++) {
    for (int j = i; j < n; j++) {
      if (v[i] > v[j]) {
        int tmp = v[i];
        v[i] = v[j];
        v[j] = tmp;
      }
    }
    cout << v[i];
  }
  while (n != 1) {
    v[0] = (v[0] + v[1]) / 2;
    for (int i = 2; i < n; i++) {
      v[i - 1] = v[i];
    }
    n--;
  }
  cout << v[0];
}
