#include <bits/stdc++.h>
using namespace std;
double p[110], ans, dp[110];
int n, a[110];
int main() {
  scanf("%d", &n);
  for (int i = 0; i <= n; i++) scanf("%lf", &p[i]);
  for (int i = 0; i <= n; i++) a[i] = abs(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,
                1.0 * (1.0 * a[i] * p[j] + 1.0 * a[j] * p[i]) / (a[i] + a[j]));
  printf("%.10lf", ans);
  return 0;
}
