#include <bits/stdc++.h>
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math")
#pragma GCC target( \
    "sse,sse2,sse3,ssse3,sse4.1,sse4.2,avx,avx2,popcnt,tune=native")
using namespace std;
namespace _c {
const double pi = acos(-1.0);
namespace min {
const int i8 = -128;
const int i16 = -32768;
const int i = -2147483647 - 1;
const long long l = -9223372036854775807LL - 1;
}  // namespace min
namespace max {
const int i8 = 127;
const int i16 = 32767;
const int i = 2147483647;
const long long l = 9223372036854775807LL;
}  // namespace max
}  // namespace _c
namespace _f {
template <typename T>
inline const T gcd(T m, T n) {
  while (n != 0) {
    T t = m % n;
    m = n;
    n = t;
  }
  return m;
}
template <typename T>
inline const T max(const T &a, const T &b) {
  return a > b ? a : b;
}
template <typename T>
inline const T min(const T &a, const T &b) {
  return a < b ? a : b;
}
template <typename T>
inline const T abs(const T &a) {
  return a > 0 ? a : -a;
}
}  // namespace _f
namespace io {
template <typename T>
inline void read(T &t) {
  register T res = 0, neg = 1;
  char c = getchar();
  for (; !isdigit(c); c = getchar()) {
    if (c == '-') {
      neg = -1;
    }
  }
  for (; isdigit(c); c = getchar()) {
    res = res * 10 + c - '0';
  }
  t = res * neg;
}
inline int in() {
  register int T;
  read(T);
  return T;
}
inline long long in_ll() {
  register long long T;
  read(T);
  return T;
}
}  // namespace io
int n;
double a[110], ans;
int main() {
  scanf("%d", &n);
  for (int i = 0; i <= n; i++) {
    scanf("%lf", a + i);
  }
  if (~n & 1) {
    ans = a[n / 2];
  }
  for (int i = 0; i * 2 <= n; i++) {
    for (int j = n; j > n / 2; j--) {
      ans = _f::max(ans,
                    ((n - 2 * i) * a[j] + (2 * j - n) * a[i]) / (2 * (j - i)));
    }
  }
  printf("%.9lf\n", ans);
  return 0;
}
