#include <bits/stdc++.h>
using namespace std;
inline int read() {
  register int x = 0, q = 0;
  register char ch = getchar();
  while (ch < '0' || ch > '9') q = ch == '-' ? 1 : q, ch = getchar();
  while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
  return q ? -x : x;
}
int n;
double val[110], Max;
int main() {
  n = read();
  for (register int i = 0; i <= n; ++i) scanf("%lf", &val[i]);
  for (register int i = n / 2 + 1; i <= n; ++i)
    for (register int j = 0; j <= n / 2; ++j) {
      int x = 2 * i - n, y = n - 2 * j, t = x * y;
      Max = max(Max, (1.0 * x * val[j] + 1.0 * y * val[i]) / (x + y));
    }
  printf("%.9lf", Max);
}
