#include<bits/stdc++.h>
using namespace std;

int main(){
  int n;
  cin >> n;
  int a[n];
  for(int i = 0;i<n;i++){
    cin >> a[i];
  }
  sort(a,a+n);
  double d = (double)(a[0]+a[1])/2;
  for(int i = 2;i<n;i++){
    d = (d+a[i])/2;
  }
  cout << d << endl;
}