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