#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  int v;
  vector<int> vs;
  for (int(i) = 0; (i) < N; (i)++) {
    cin >> v;
    vs.push_back(v);
  }
  sort((vs).begin(), (vs).end());
  double value = 0;
  double temp = (double)(vs[0] + vs[1]) / 2;
  for (int i = 2; i < N; i++) {
    value = (double)(temp + vs[i]) / 2;
    temp = value;
  }
  cout << value;
  return 0;
}
