#include <bits/stdc++.h>
int desc(const void *a, const void *b) {
  double x;
  int k;
  x = *(double *)b - *(double *)a;
  k = x > 0 ? -1 : 1;
  return k;
}
int main(void) {
  int i, n;
  double v[1001];
  scanf("%d", &n);
  for (i = 0; i < n; i++) {
    scanf("%le", &v[i]);
  }
  qsort(v, n, sizeof(double), desc);
  for (i = n - 1; i > 0; i--) {
    v[i - 1] = (v[i - 1] + v[i]) / (double)2;
    qsort(v, i, sizeof(double), desc);
  }
  printf("%le\n", v[0]);
  return 0;
}
