#include <bits/stdc++.h>   using namespace std;   int n;   double p[100008];   struct Tprogram {     void open() {       freopen( 1.in ,  r , stdin);       freopen( 1.out ,  w , stdout);     }     void close() {}     void init() {       scanf( %d , &n);       for (int i = 0; i <= n; i++) scanf( %lf , &p[i]);     }     void work() {       double ans = 0;       for (int i = 0; i <= n >> 1; i++)         for (int j = (n >> 1) + 1; j <= n; j++)           ans = ((p[i] * (2 * j - n) + p[j] * (n - 2 * i)) / (2 * j - 2 * i) > ans                      ? (p[i] * (2 * j - n) + p[j] * (n - 2 * i)) / (2 * j - 2 * i)                      : ans);       printf( %.10lf n , ans);     }   } Program;   int main() {     Program.init();     Program.work();     return 0;   }   