import java.util.Scanner;

public class Hack44_first {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner s = new Scanner(System.in);
		int size = s.nextInt();
		int[] arr = new int[size];
		for(int i = 0;i<size;i++){
			arr[i] = s.nextInt();
		}
		int count1 = 0, count2 = 0, count3 = 0, max = 0;
		for(int i = 0;i<size-1;i++){
			count1 = 0;
			count2 = 0;
			count3 = 0;
			for(int j = i+1;j<size;j++){
				if((arr[i]-arr[j])==0){
					count1++;
				}
				else if((arr[i]-arr[j])==1){
					count2++;
				}
				else if((arr[i]-arr[j])==-1){
					count3++;
				}		
			}
			max =Math.max(max,Math.max(count1+count2, count1+count3));
		}
		System.out.println(1+max);			
	}

}