#include <bits/stdc++.h>
using namespace std;
const int maxn = 205;
int n;
double p[maxn], c[maxn], ans;
signed main() {
  ios::sync_with_stdio(false);
  cin >> n;
  for (int i = 0; i <= n; ++i) {
    cin >> p[i];
  }
  for (int i = 0; i <= n; ++i) {
    c[i] = fabs(n - 2 * i);
  }
  for (int i = 0; i <= (n - 1) / 2; ++i) {
    for (int j = (n - 1) / 2 + 1; j <= n; ++j) {
      ans = max(ans, (c[i] * p[j] + c[j] * p[i]) / (c[i] + c[j]));
    }
  }
  printf("%.9lf\n", ans);
  return 0;
}
