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 Julia (0.5.0) (judge verdict: Accepted)

parseInt(x::String) = parse(Int, x)
parseInt(x::SubString{String}) = parse(Int, x)
parseInt(x::Char) = parse(Int, x)
parseInt(x::Float64) = trunc(Int, x)
parseFloat(x::String) = parse(Float64, x)
parseFloat(x::Int) = trunc(Float64, x)
parseFloat(x::SubString{String}) = parse(Float64, x)
parseFloat(x::Char) = parse(Float64, x)
parseMap(x::Array{SubString{String},1}) = map(parseInt, x)

function main()
    n=parseInt(readline())
    a=parseMap(split(readline()))
    num=Vector{Int}()
    for i in a
        push!(num,i+1,i,i-1)
    end
    sort!(num)
    ans=0
    cnt=1
    for i in 2:3n+1
        if i==3n+1 || num[i]!=num[i-1]
            ans=max(ans,cnt)
            cnt=1
        else
            cnt+=1
        end
    end
    println(ans)
end
main()