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 min = -1;
        int maxnum = 0;
        int result = 0;
        List<Integer> nums = new ArrayList<>();
        for(int i=0;i<n;i++){
            //System.out.println(a[i]);
            if(min == -1)
            {
                nums.add(a[i]);
                //System.out.println(nums);
                maxnum++;
                min = a[i];
            }
            else if(a[i] - min <= 1)
            {
                nums.add(a[i]);
                //System.out.println(nums);
                maxnum++;
            }
            else
            {
                if(maxnum > result)
                    result = maxnum;
                for(int j=0;j<nums.size();j++)
                {
                    if(a[i] - nums.get(j) > 1)
                    {
                        nums.remove(j);
                        //System.out.println(nums);
                    }
                    else
                        break;
                }
                if(nums.size() > 0)
                    min = nums.get(0);
                else
                    min = -1;
                nums.add(a[i]);
                maxnum = nums.size();
            }
        }
        if(maxnum > result)
            result = maxnum;
        System.out.println(result);
    }
}