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: Wrong Answer)

N = gets.to_i
ary = gets.split.map(&:to_i)
hash = {}
ary.each do |n|
    hash[n] = hash[n].to_i + 1
end
l = hash.sort
max_vals = {}
l.each_with_index do |a, i|
    pre = i==0 ? 0 : l[i-1][1]
    post = i==l.size-1 ? 0 : l[i+1][1]
    max_vals[l[i][0]] = pre + l[i][1] + post
end
puts max_vals.max{|a, b| a[1]<=>b[1]}[1]