#include <bits/stdc++.h>
using namespace std;
float avg(int a, int b) {
  float ans = (float)a + (float)b;
  return ans / 2;
}
int main() {
  int n;
  cin >> n;
  int arr[n];
  for (int i = 0; i < n; i++) cin >> arr[i];
  sort(arr, arr + n);
  float g = arr[0];
  for (int i = 1; i < n - 1; i++) {
    g = avg(g, arr[i]);
  }
  cout << avg(g, arr[n - 1]) << endl;
  return 0;
}
