#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double p[103], res = 0;
  scanf("%d", &n);
  for (int i = 0; i <= n; i++) scanf("%lf", &p[i]);
  if (n % 2 == 0) res = p[n / 2];
  for (int i = 0; 2 * i <= n; i++) {
    for (int j = (n + 1) / 2.0; j <= n; j++) {
      double y = (n / 2.0 - i) / (j - i), x = 1 - y;
      if (x * p[i] + y * p[j] > res) res = x * p[i] + y * p[j];
    }
  }
  printf("%.10lf\n", res);
  return 0;
}
