#include <bits/stdc++.h>
using namespace std;
int main() {
  int b;
  int N;
  cin >> N;
  vector<float> A(N);
  for (int i = 0; i < N; ++i) {
    cin >> A[i];
  }
  sort(A.begin(), A.end());
  for (int i = 0; i < N - 1; ++i) {
    b = (A[i] + A[i + 1]) / 2.0;
    A[i + 1] = b;
  }
  cout << b;
  return 0;
}
