#include <bits/stdc++.h>
const int inf = 1000000005;
using namespace std;
const double eps = 1e-9;
int m, i, j, k, n;
double p[1001], ans;
int main() {
  cin >> n;
  for (i = 0; i <= n; i++) {
    cin >> p[i];
  }
  ans = 0.0;
  if (n % 2 == 0) ans = p[n / 2];
  for (i = 0; i <= n; i++)
    if (2 * i < n)
      for (j = 0; j <= n; j++)
        if (2 * j > n) {
          double a = 1.0 * (n - 2 * i) / (2 * j - n);
          ans = max(ans, (p[i] + a * p[j]) / (1 + a));
        }
  printf("%.10lf\n", ans);
  return 0;
}
