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 Pascal (FPC 2.6.2) (judge verdict: Accepted)

program ec12;
var 
	n,m,i,j,x,max:longint;
	a:array[0..100002] of longint;
begin 
	fillchar(a,sizeof(a),0);
	readln(n);
	for i:=1 to n do 
	begin
		read(x);
		inc(a[x]);
	end;
	max:=a[0]+a[1];
	for i:=1 to 100000 do 
	begin 
		if max<a[i]+a[i-1]+a[i+1] then 
		max:=a[i]+a[i-1]+a[i+1];
	end;
	writeln(max);
end.