#include <bits/stdc++.h>
int compare(const void *a, const void *b) { return *(int *)b - *(int *)a; }
int main(void) {
  int N, last_index;
  double v[50];
  scanf("%d", &N);
  for (int i = 0; i < N; i++) {
    scanf("%lf", &(v[i]));
  }
  qsort(v, N, sizeof(double), compare);
  last_index = N - 1;
  while (last_index > 0) {
    v[last_index - 1] = (v[last_index] + v[last_index - 1]) / 2;
    v[last_index] = 0;
    last_index--;
  }
  printf("%f", v[0]);
  return 0;
}
