#include <bits/stdc++.h>
using namespace std;
int n;
double c[205], p[205], ans;
int main() {
  cin >> n;
  for (int i = 0; i <= n; i++) scanf("%lf", &p[i]);
  for (int i = 0; i <= n; i++) c[i] = fabs(n - 2 * i);
  for (int i = 0; i <= (n - 1) / 2; i++)
    for (int j = (n - 1) / 2 + 1; j <= n; j++)
      ans = max(ans, (c[j] * p[i] + c[i] * p[j]) / (c[j] + c[i]));
  printf("%.12lf", ans);
  return 0;
}
