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 max = 0;

        int holdj;
        for (int j = 0; j < a.length; ) {
            int size = 0;
            int i = 0;
            holdj = 0;
            for (i = j; i < a.length; i++) {
                int diff = Math.abs(a[j] - a[i]);
                if (diff == 0) {
                    size++;
                } else if (diff == 1) {
                    size++;
                    if(holdj == 0){
                        holdj = i;
                    }

                } else {
                    if (size > max) {
                        max = size;
                    }
                    if(holdj == 0){
                        j = i;
                    }else{
                        j = holdj ;
                    }

                    break;
                }
            }
            if (i == a.length) {
                if (size > max) {
                    max = size;
                }
                break;
            }
        }


        System.out.print( max);
    }
}