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

int main()
{
  int n;
  cin>>n;
  int *ar = new int[n];
  for(int i = 0;i<n;i++)
   	cin>>ar[i];
  for(int i = n-1;i > 0;i--)
  {
    for(int j = 0;j<i;j++)
    {
      if(ar[j] > ar[j+1])
      {
        int temp = ar[j];
        ar[j] = ar[j+1];
        ar[j+1] = temp;
      }
    }
  }
  float sum = (ar[0] + ar[1])/2.0;
  for(int i = 2;i<n-1;i++)
  {
    sum = (sum + ar[i])/2.0;
  }
  cot<<sum;
  return 0;
}
    