#include<iostream>
#include<algorithm>
using namespace std;

int main(){
  int N;cin >> N;
  double v[50];
  for(int i = 0;i < N;++i)
    cin >> v[i];
  sort(v, v + N);
  for(int i = 0;i < N - 1;++i){
    v[i + 1] = (v[i] + v[i + 1]) / 2;
  }
  cout << v[N - 1];
}
