#include <bits/stdc++.h>
using namespace std;
int a[2333], n, s1 = 2, s2 = 3;
double b[2333];
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a[i];
  sort(a + 1, a + n + 1);
  b[s1] = ((double)(1.0 * a[1]) + (double)(1.0 * a[2])) / 2;
  while (s2 < n) {
    b[s2] = ((double)(1.0 * b[s1]) + (double)(1.0 * a[s2])) / 2.0;
    s1++;
    s2++;
  }
  printf("%.6lf", b[n]);
  return 0;
}
