#include <bits/stdc++.h>
int main(void) {
  int n, i, j, waru_2noi1jou = 1;
  double v[50];
  double sum = 0, temp;
  scanf("%d", &n);
  for (i = 0; i < n; i++) {
    scanf("%lf", &v[i]);
  }
  for (i = 0; i < n; i++) {
    for (j = i + 1; j < n; j++) {
      if (v[i] < v[j]) {
        temp = v[j];
        v[j] = v[i];
        v[i] = temp;
      }
    }
  }
  for (i = 0; i < n; i++) {
    if (i != n - 1) {
      waru_2noi1jou *= 2;
    }
    sum += v[i] / waru_2noi1jou;
  }
  printf("%f\n", sum);
  return 0;
}
