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

int main() {
  int N;
  vector<int> v(N);
  
  for (int i = 0; i < N; i++) {
    cin >> v[i];
  }
  
  sort(v.begin(), v.end());
  
  for (int i = 0; i < N-1; i++) {
    if (i == 0) double avg = v[0];
    
    avg = ( ((double) avg)+((double) v[i+1]) )/2;
  }
  
  cout << avg << endl;
  
}
