#include <bits/stdc++.h>
using namespace std;
long double p[101];
int main() {
  int N;
  long double ans = 0;
  cin >> N;
  for (int i = 0; i <= N; i++) cin >> p[i];
  for (int i = 0; i <= N - 1 >> 1; i++)
    for (int j = (N >> 1) + 1; j <= N; j++)
      if ((p[i] * (2 * j - N) + p[j] * (N - 2 * i)) / (-2 * i + 2 * j) > ans)
        ans = (p[i] * (2 * j - N) + p[j] * (N - 2 * i)) / (-2 * i + 2 * j);
  if ((N & 1) == 0) ans = max(ans, p[N >> 1]);
  cout << fixed << setprecision(9) << ans;
  return 0;
}
