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

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