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();
        }
        int[] b = new int[n];
        int[] c = new int[n];
        int num = 0;
        for(int i =0 ; i < n; i++){
            b[i] = 0;
            c[i] = 0;
            for(int j=0; j<n; j++){
                num = a[i] - a[j];
                if(num == 0 || num == 1)
                    b[i]++;
                if(num == 0 || num == -1)
                    c[i]++;
            }
        }
        num = 0;
        for(int i=0; i< n; i++){
            if(b[i]>num)
                num = b[i];
            if(c[i]>num)
                num = c[i];
        }
        System.out.println(num);
    }
}