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

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a = new int[n];
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
        }
        System.out.println(get(a));
    }
    public static int get(int[]a){
    	Arrays.sort(a);
    	int c = 1;
    	int max = Integer.MIN_VALUE;
    	int tmp = a[0];
    	for(int i=0;i<a.length-1;i++){
    		if(Math.abs(tmp-a[i+1])<=1){
    			c++;
    		}else{
    			if(c>max){
    				max = c;
    			}
    			tmp = a[i+1];
    			c = 1;
    		}
    	}
    	if(c>max)
    		max=c;
    	return max;
    }
}