#include <bits/stdc++.h>
using namespace std;
double p[101];
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i <= n; i++) scanf("%lf", &p[i]);
  double ans = 0;
  for (int i = 0; i <= n; i++) {
    if (n - 2 * i == 0) ans = max(ans, p[i]);
    if (n - 2 * i <= 0) continue;
    for (int j = i + 1; j <= n; j++) {
      if (n - 2 * j >= 0) continue;
      int a = 2 * j - n;
      int b = n - 2 * i;
      ans = max(ans, (a * p[i] + b * p[j]) / (a + b));
    }
  }
  printf("%.10lf\n", ans);
  return 0;
}
