Problem:
Score : 300 points

Problem Statement

You are given an integer sequence of length N, a_1,a_2,...,a_N.

For each 1≤i≤N, you have three choices: add 1 to a_i, subtract 1 from a_i or do nothing.

After these operations, you select an integer X and count the number of i such that a_i=X.

Maximize this count by making optimal choices.

Constraints

1≤N≤10^5

0≤a_i<10^5 (1≤i≤N)

a_i is an integer.

Input

The input is given from Standard Input in the following format:

N
a_1 a_2 .. a_N

Output

Print the maximum possible number of i such that a_i=X.

Sample Input 1

7
3 1 4 1 5 9 2

Sample Output 1

4

For example, turn the sequence into 2,2,3,2,6,9,2 and select X=2 to obtain 4, the maximum possible count.

Sample Input 2

10
0 1 2 3 4 5 6 7 8 9

Sample Output 2

3

Sample Input 3

1
99999

Sample Output 3

1

Solution in Ruby (2.3.3) (judge verdict: Accepted)

n = gets.chomp.to_i
a = gets.chomp.split(" ").map(&:to_i)
plus = a.map{|e| e+1}
minus = a.map{|e| e-1}
arr = a + plus + minus
list = Hash.new(0)
arr.each do |e|
    list[e] += 1
end
x = list.max{|x, y| x[1] <=> y[1]}
ans = 0
a.each do |e|
    tmp = nil
    if e < x[0]
        tmp = e + 1
    elsif e > x[0]
        tmp = e - 1
    else
        tmp = e
    end
    ans += 1 if tmp == x[0]
end
puts ans