import java.util.*;
import java.math.*;
class picking_numbers
{
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		ArrayList<Integer> al = new ArrayList<Integer>(n);
		
		int i, j;
		for(i = 0; i < n; ++i)
			al.add(sc.nextInt());
		
		Collections.sort(al);
		int max = 0, count = 0;
		
		for(i = 0; i < n - 1; ++i)
		{
			count = 1;
			for(j = i+1; j < n; ++j)
			{
				if(i != j)
				{
					if(Math.abs(al.get(i) - al.get(j)) <= 1)
						++count;
					else
						break;
				}
			}
			max = Integer.max(max, count);
		}
		System.out.println(max);
		
	}

}