N different natural numbers are given. If you select four different ones and set them as $ A $, $ B $, $ C $, $ D $, the following formula

$ \ Frac {A + B} {C --D} $



I want to find the maximum value of.




Given N different natural numbers, choose 4 different from them and create a program to find the maximum value of the above formula.



Input

The input is given in the following format.


N
a1 a2 ... aN


The number N (4 ≤ N ≤ 1000) of natural numbers is given in the first line. The value ai (1 ≤ ai ≤ 108) of each natural number is given in the second line. However, the same natural number does not appear more than once (ai ≠ aj for i ≠ j).

Output

Outputs the maximum value of the above formula as a real number for a given N natural numbers. However, the error must not exceed plus or minus 10-5.

Examples

Input

10
1 2 3 4 5 6 7 8 9 10


Output

19.00000


Input

5
22 100 42 3 86


Output

9.78947


Input

6
15 21 36 10 34 5


Output

18.00000


Input

4
100000 99999 8 1


Output

28571.285714
n = int(input())
alst = sorted(list(map(int, input().split())))

ans = 0
for i in range(n):
  for j in range(i + 1, n):
    c = alst[j]
    d = alst[i]
    if j <= n - 3:
      a, b = alst[n - 1], alst[n - 2]
    elif i >= n - 2:
      a, b = alst[n - 3], alst[n - 4]
    elif j == n - 1 and i == n - 3:
      a, b = alst[n - 2], alst[n - 4]
    elif j == n - 2 and i == n - 3:
      a, b = alst[n - 1], alst[n - 4]
    elif j == n - 1 and i == n - 4:
      a, b = alst[n - 2], alst[n - 3]
    elif j == n - 2 and i == n - 4:
      a, b = alst[n - 1], alst[n - 3]
    ans = max(ans, (a + b) / (c - d))
print(ans)
