#include <bits/stdc++.h>
using namespace std;
int n;
double ans, p[205];
double f[1005][305];
int main() {
  scanf("%d", &n);
  for (int i = 0; i <= n; ++i) scanf("%lf", &p[i]);
  memset(f, -63, sizeof(f));
  f[0][n] = 0;
  for (int i = 1; i <= 1000; ++i)
    for (int j = 0; j <= n + n; ++j)
      for (int k = 0; k <= j && k <= n; ++k) {
        int q = n - k - k;
        if (j + q >= 0 && j + q <= n + n)
          f[i][j + q] = max(f[i][j + q], f[i - 1][j] + p[k]);
      }
  for (int i = 1; i <= 1000; ++i) ans = max(ans, f[i][n] / i);
  printf("%.10lf\n", ans);
  return 0;
}
