#include <bits/stdc++.h>
int main(void) {
  int n;
  char str1[5], str2[5000];
  char *s;
  fgets(str1, sizeof(str1), stdin);
  n = atof(str1);
  double a[n], b;
  fgets(str2, sizeof(str2), stdin);
  int i, j, k;
  i = 0;
  s = strtok(str2, " ");
  while (s != NULL) {
    a[i] = atof(s);
    i++;
    s = strtok(NULL, " ");
  }
  for (i = 0; i < n; i++) {
    b = 0;
    for (j = i; j < n; j++) {
      if (a[j] > b) {
        b = a[j];
        k = j;
      }
    }
    a[k] = a[i];
    a[i] = b;
  }
  double sum;
  sum = 0;
  for (i = 0; i < n; i++) {
    sum += a[i] / (pow(2.0, i + 1));
  }
  printf("%lf\n", sum);
  return 0;
}
