#include <bits/stdc++.h>
int main(void) {
  int n, v[1000] = {0}, ex;
  int i, j;
  double max = 0, sum = 0;
  scanf("%d", &n);
  for (i = 0; i < n; i++) {
    scanf("%d", &v[i]);
  }
  for (i = 0; i < n; i++) {
    for (j = i; j < n; j++) {
      if (v[i] < v[j]) {
        ex = v[i];
        v[i] = v[j];
        v[j] = ex;
      }
    }
  }
  sum = (double)v[n] / (double)pow(2, n - 1);
  for (i = 1; i < n - 1; i++) {
    sum += (double)v[i] / (double)pow(2, i + 1);
  }
  printf("%lf", sum);
  return 0;
}
