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)

var a:array[0..100050]of longint;
    ans:longint;
    i:longint;
    n:longint;
    mx,x:longint;
function max(a,b:longint):longint;
begin
  if a>b then exit(a) else exit(b);
end;
begin
  read(n);
  for i:=1 to n do
  begin
    read(x);
    inc(a[x]);
    if x>mx then mx:=x;
  end;
  ans:=a[0]+a[1];
  for i:=1 to mx do
  ans:=max(ans,a[i-1]+a[i]+a[i+1]);
  writeln(ans);
end.