#include <bits/stdc++.h>
using namespace std;
bool ee(int a, int b) { return (a < b); }
int main() {
  int n;
  double s;
  cin >> n;
  int v[n];
  for (int i = 0; i < n; i++) cin >> v[i];
  sort(v, v + n, ee);
  s = (v[0] + v[1]) / 2;
  for (int i = 2; i < n - 1; i++) {
    s = (s + v[i]) / 2;
  }
  cout << s;
  return 0;
}
