#include <bits/stdc++.h>
using namespace std;
int arr[55];
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", arr + i);
  sort(arr, arr + n);
  long double res = (arr[0] + arr[1]) / 2;
  for (int i = 2; i < n; i++) {
    res = (res + arr[i]) / 2;
  }
  printf("%.6Lf\n", res);
  return 0;
}
