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