#include <bits/stdc++.h>
using namespace std;
int n, m;
double a[1001], b[1001];
int main() {
  scanf("%d", &n);
  double mx = 0;
  for (int i = 0; i <= n; ++i) {
    scanf("%lf", &a[i]);
    b[i] = fabs(n - 2 * i);
  }
  for (int i = 0; i <= (n - 1) / 2; ++i) {
    for (int j = (n - 1) / 2 + 1; j <= n; ++j) {
      mx = max(mx, (b[j] * a[i] + b[i] * a[j]) / (b[j] + b[i]));
    }
  }
  printf("%.15lf", mx);
}
