#include <bits/stdc++.h>
using namespace std;
int n;
double p[105], ans;
int main() {
  cin >> n;
  for (int i = 0; i <= n; i++) scanf("%lf", &p[i]);
  for (int i = 0; i <= (n - 1) / 2; i++)
    for (int j = n / 2 + 1; j <= n; j++)
      ans =
          max(ans, ((2 * j - n) * p[i] + (n - 2 * i) * p[j]) / (2 * j - 2 * i));
  if (n % 2 == 0) ans = max(ans, p[n / 2]);
  printf("%.10lf\n", ans);
  return 0;
}
