#include <bits/stdc++.h>
using namespace std;
double arr[50];
int main() {
  int N;
  scanf("%d", &N);
  for (int i = 0; i < N; i++) scanf("%lf", &arr[i]);
  double ans = 0, res;
  sort(arr, arr + N);
  do {
    res = arr[0];
    for (int i = 1; i < N; i++) {
      res = (res + arr[i]) / 2;
    }
    ans = max(ans, res);
  } while (next_permutation(arr, arr + N));
  printf("%.6lf\n", ans);
  return 0;
}
