import java.util.Arrays;
import java.util.Scanner;

class picking_number {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc=new Scanner(System.in);
		int n,i=0,j=0,count=0;
		n=sc.nextInt();
		if(n>=2)
		{
			int arr[]=new int[n],arr_count[]=new int[n];
			for(i=0;i<n;i++)
			{
				arr[i]=sc.nextInt();
			}
			Arrays.sort(arr);
			for(i=0;i<n;i++)
			{
				count=0;
				for(j=0;j<n && i!=j;j++)
				{
					if(Math.abs(arr[i]-arr[j])==1 || Math.abs(arr[i]-arr[j])==0 )
					{
						count++;
						//System.out.println(arr[i]+"  "+arr[j]+"  "+count);
					}
				}
				//System.out.println();
				arr_count[i]=count;
			}
			Arrays.sort(arr_count);
			System.out.println(arr_count[n-1]+1);
		}
	}

}