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.to_i
a=Array.new(n)
a=gets.chomp.split(" ").map(&:to_i)
=begin
for i in 0..a.length-1
    a[i]=a[i].to_i
end
=end

b=a.sort

maxcnt=0
maenopib=0

for i in 0..n-1
    cnt=0
    pib=b[i]
    if i!=0 && pib==b[i-1]
        next
    end

    for j in i..n-1
        if b[j]==pib || b[j]==pib+1 || b[j]==pib+2
            cnt+=1
        else
            break
        end
    end
    if cnt>maxcnt
        maxcnt=cnt
    end
end
print maxcnt