#include <bits/stdc++.h>
int v[55];
using namespace std;
int main() {
  int n;
  float ans = 0;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> v[i];
  }
  sort(v + 1, v + n + 1);
  ans = ((float)(v[1] + v[2])) / 2;
  for (int i = 3; i <= n; i++) {
    ans = (ans + v[i]) / 2;
  }
  cout << ans << endl;
  return 0;
}
