#include <bits/stdc++.h>
using namespace std;
const long double PI = acos(-1.0);
const int N = 111;
int n;
double a[N];
int pos[N];
int main() {
  cin >> n;
  for (int i = 0; i < (int)(n + 1); ++i) cin >> a[i];
  double res = 0;
  if (n % 2 == 0) res = a[n / 2];
  for (int i = 0; 2 * i < n; i++) {
    for (int j = n; 2 * j > n; j--) {
      int got = n - 2 * i;
      int need = 2 * j - n;
      double val1 = a[i], val2 = a[j];
      res = max(res, (val1 * need + val2 * got) / (got + need));
    }
  }
  cout << fixed << setprecision(12) << res << endl;
  return 0;
}
