#include <bits/stdc++.h>
void selection_sort(int value[], int array_size);
void swap(int *x, int *y);
int main() {
  int n;
  scanf("%d", &n);
  int value[n];
  for (int i = 0; i < n; i++) {
    scanf("%d", &value[i]);
  }
  selection_sort(value, n);
  double sum = (value[0] + value[1]) / 2;
  for (int j = 2; j < n; j++) {
    sum = (sum + value[j]) / 2;
  }
  printf("%f\n", sum);
}
void swap(int *x, int *y) {
  int temp;
  temp = *x;
  *x = *y;
  *y = temp;
}
void selection_sort(int value[], int array_size) {
  int i, j, min_index;
  for (i = 0; i < array_size - 1; i++) {
    min_index = i;
    for (j = i + 1; j < array_size; j++) {
      if (value[j] < value[min_index]) {
        min_index = j;
      }
    }
    swap(&value[min_index], &value[i]);
  }
}
