#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:64000000")
using namespace std;
const int INF = ((1 << 31) - 1);
const long long LLINF = (((1LL << 63) - 1LL));
const double eps = 1e-9;
const double PI = 3.14159265358979323846;
const int maxN = 201;
double max_sum[maxN][maxN];
double calc[maxN][maxN];
int n;
double p[maxN];
double getMaxSum(int one_year, int len) {
  if (one_year > 2 * n) return getMaxSum(2 * n, len);
  if (len == 0) {
    if (one_year == n) return 0.0;
    return -1e30;
  }
  if (calc[one_year][len]) return max_sum[one_year][len];
  double res = -1.0;
  for (int to_second_use = 0; to_second_use <= one_year && to_second_use <= n;
       ++to_second_use) {
    res = max(res, p[to_second_use] +
                       getMaxSum(one_year - to_second_use + (n - to_second_use),
                                 len - 1));
  }
  calc[one_year][len] = true;
  return max_sum[one_year][len] = res;
}
bool can(double avg) {
  static double am[201][201];
  for (int i = 0; i <= n + n; ++i) {
    for (int j = 0; j <= n + n; ++j) {
      am[i][j] = 1e60;
    }
  }
  for (int i = 0; i <= n + n; ++i) {
    for (int t = 0; t <= n; ++t) {
      int ni = i - t + (n - t);
      if (ni >= 0 && ni <= n + n) am[i][ni] = avg - p[t];
    }
  }
  for (int k = 0; k <= n + n; ++k)
    for (int i = 0; i <= n + n; ++i)
      for (int j = 0; j <= n + n; ++j) {
        am[i][j] = min(am[i][j], am[i][k] + am[k][j]);
      }
  for (int i = 0; i <= n + n; ++i)
    if (am[i][i] < 0) return true;
  return false;
}
int main() {
  cin >> n;
  for (int i = 0; i <= n; ++i) scanf("%lf", &p[i]);
  double lower = 0.0;
  double upper = 1.0;
  for (int it = 0; it < 50; ++it) {
    double middle = (lower + upper) / 2.0;
    if (can(middle))
      lower = middle;
    else
      upper = middle;
  }
  printf("%0.18lf\n", lower);
  return 0;
  double res = 0.0;
  for (int len = 1; len <= 2 * n; ++len) {
    for (int one_year = 0; one_year <= n; ++one_year) {
      res = max(res, getMaxSum(n, len) / len);
    }
  }
  printf("%0.18lf\n", res);
  return 0;
}
