#include <bits/stdc++.h>
using namespace std;
int INF = 1000000007;

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