#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 25, M = 1e6 + 25, oo = 1e9 + 7, mxmsk = 1 << 16;
const long long OO = 1e18 + 25;
int n, k, q, a[N], x, p = 2;
double ans;
int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", a + i);
  sort(a, a + n);
  for (int i = n - 1; i > 0; i--) {
    ans += 1.0 * a[i] / p;
    p *= 2;
  }
  ans += 1.0 * a[0] / (p / 2);
  printf("%.6lf", ans);
  return 0;
}
