#include <bits/stdc++.h>
using namespace std;
double p[107];
int main() {
  int n, i, j, x1, x2;
  double ans;
  scanf("%d", &n);
  for (i = 0; i <= n; i++) scanf("%lf", &p[i]);
  ans = 0;
  for (i = 0; i <= (n - 1) / 2; i++)
    for (j = (n + 2) / 2; j <= n; j++)
      ans =
          max(ans, (p[i] * (2 * j - n) + p[j] * (n - 2 * i)) / (2 * j - 2 * i));
  printf("%.9lf", max(ans, n % 2 == 0 ? p[n / 2] : 0));
  return 0;
}
