#include <bits/stdc++.h>
using namespace std;
int n;
float arr[100000];
float maxs = 0;
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) {
    scanf("%f", &arr[i]);
  }
  float maxs = 0;
  do {
    float maxs2 = arr[1];
    for (int i = 2; i <= n; i++) {
      maxs2 = (maxs2 + arr[i]) / 2;
    }
    if (maxs < maxs2) {
      maxs = maxs2;
    }
  } while (prev_permutation(arr + 1, arr + n + 1));
  printf("%f", maxs);
  return 0;
}
