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 OCaml (4.02.3) (judge verdict: Accepted)

module IMap=Map.Make(struct type t=int let compare=compare end);;
Scanf.(Array.(scanf" %d"@@ fun n->
	let m = init n(fun _->scanf" %d"@@fun v->v)
	|> fold_left(fun m v->IMap.add v (1+try IMap.find v m with Not_found -> 0) m) IMap.empty
	in IMap.fold(fun v c r->
		let p,q=(try IMap.find (v-1) m with Not_found->0),(try IMap.find (v+1) m with Not_found->0)
		in max r (p+q+c)) m 0 |> print_int))