import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

   public static int diff(int a[])
	{
		Arrays.sort(a);
		int one[]=new int[a.length];
		int second[]=new int[a.length];

		int count1[]=new int[a.length];
		int count2[]=new int[a.length];
		int count3[]=new int[a.length];
		for(int i=0;i<a.length;i++)
		{
			for(int j=0;j<a.length;j++)
			{
				
					if(a[i]==a[j]-1)
						count1[i]++;
					if(a[i]==a[j]+1)
						count2[i]++;
					if(a[i]==a[j]&&i!=j)
						count3[i]++;
					
				
				
			}
			one[i]+=count1[i]+count3[i];
			second[i]+=count2[i]+count3[i];

		}
		Arrays.sort(one);
		Arrays.sort(second);
		
		
		return Math.max(one[a.length-1],second[a.length-1])+1;

	}

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner s=new Scanner(System.in);
		int size=s.nextInt();
		int a[]=new int[size];
		for(int i=0;i<size;i++)
		{
			a[i]=s.nextInt();
		}
		System.out.println(diff(a));

	}
}