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();
        }
        Arrays.sort(a);
        int n1=1,n2=1;
        int f=a[0];
        int i=1;
        while(i<a.length){
            if(a[i]<=f+1){
                n2++;
            }
            else{
                f=a[i];
                if(n2>n1){
                    n1=n2;
                }
                n2=1;
            }
            i++;
        }
        if(n2>n1){
            n1=n2;
        }
        System.out.println(n1);
    }
}