#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  scanf("%d ", &N);
  vector<int> v(N);
  for (int i = 0; i < N; i++) {
    scanf("%d", &v[i]);
  }
  sort(v.begin(), v.end());
  float max = 0;
  do {
    float sum = (float)v[0];
    for (int i = 1; i < N; i++) {
      sum = (sum + (float)v[i]) / 2;
    }
    if (max < sum) max = sum;
  } while (next_permutation(v.begin(), v.end()));
  printf("%f", max);
}
