#include <bits/stdc++.h>
using namespace std;
const int MAXN = 100;
double d[2 * MAXN + 10][2 * MAXN + 10];
double p[MAXN + 10];
int main(void) {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < (n + 1); ++i) {
    scanf("%lf", &p[i]);
  }
  double l = 0.0, r = 1.0;
  for (int f = 0; f < (50); ++f) {
    double mid = 0.5 * (l + r);
    for (int i = 0; i < (2 * n); ++i) {
      for (int j = 0; j < (2 * n); ++j) {
        if (i >= j) {
          d[i][j] = 0.0;
        } else {
          d[i][j] = 1e6;
        }
      }
    }
    for (int i = 0; i < (2 * n); ++i) {
      for (int j = 0; j <= min(i, n); ++j) {
        int b = min(i + n - 2 * j, 2 * n - 1);
        d[i][b] = min(d[i][b], mid - p[j]);
      }
    }
    bool ok = false;
    for (int k = 0; k < (2 * n); ++k) {
      for (int i = 0; i < (2 * n); ++i) {
        for (int j = 0; j < (2 * n); ++j) {
          d[i][j] = min(d[i][k] + d[k][j], d[i][j]);
        }
      }
      for (int i = 0; i < (2 * n); ++i) {
        if (d[i][i] < -1e-10) {
          ok = true;
          break;
        }
      }
    }
    if (ok) {
      l = mid;
    } else {
      r = mid;
    }
  }
  printf("%.10lf\n", (l + r) * 0.5);
  return 0;
}
