#include <bits/stdc++.h>
using namespace std;
int gi() {
  int x = 0, w = 1;
  char ch = getchar();
  while ((ch < '0' || ch > '9') && ch != '-') ch = getchar();
  if (ch == '-') w = 0, ch = getchar();
  while (ch >= '0' && ch <= '9')
    x = (x << 3) + (x << 1) + ch - '0', ch = getchar();
  return w ? x : -x;
}
int n;
double a[105], ans = -1e9;
int main() {
  n = gi();
  for (int i = 0; i <= n; ++i) scanf("%lf", &a[i]);
  for (int i = 0, x = n; x > 0; ++i, x -= 2)
    for (int j = n, y = n; y > 0; --j, y -= 2)
      ans = max(ans, (a[i] * y + a[j] * x) / (x + y));
  if (~n & 1) ans = max(ans, a[n >> 1]);
  printf("%.10lf\n", ans);
  return 0;
}
