#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<double> V(N);
  for (size_t i = 0; i < N; i++) {
    cin >> V[i];
  }
  while (V.size() != 1) {
    sort(V.rbegin(), V.rend());
    int a = V.back();
    V.pop_back();
    int b = V.back();
    V.pop_back();
    V.push_back((double)(a + b) / (double)2.0);
  }
  cout << V[0] << endl;
  return 0;
}
