#include <iostream>
#include <vector>

using namespace std;
int main(){
  int n;
  double val;
  
  cin >> n;
  for(int i = 0; i < n; i++)
    cin >> val[i];
  
  sort(val, val + n );
  
  for(int i = 0; i + 1 != val.length; i++)
    val[i + 1] = (val[i] + val[i + 1]) / 2;
  
  cout << val[n - 1] << endl;
  
  return 0;
}
  