#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a[55];
  double m;
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  m = (a[1] + a[0]) / 2;
  if (n == 2)
    printf("%.6lf", m);
  else {
    for (int i = 2; i < n; i++) m = m / 2 + a[i] / 2;
    printf("%.6f", m);
  }
  return 0;
}
