#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  int v[1100];
  double x = 0;
  double y = 0;
  cin >> N;
  for (int i = 0; i < N; ++i) cin >> v[i];
  sort(v, v + N);
  y = (v[0] + v[1]) / 2;
  for (int i = 2; i < N; ++i) {
    y = (y + v[i]) / 2;
  }
  cout << y << endl;
}
