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();
        }
        
        if(a.length < 2) {
            System.out.println(0);
            return;
        }
        
        if(a.length == 2) {
            if(Math.abs(a[0] - a[1]) <= 1) 
                System.out.println(2);
            else
                System.out.println(0);
            return;
        }
        
        ArrayList<ArrayList<Integer>> subsets = new ArrayList<ArrayList<Integer>>();
        Arrays.sort(a);   
        
        int arrayNum = 0;
        ArrayList<Integer> newSubset = new ArrayList();
        newSubset.add(a[0]);
        subsets.add(newSubset);
        
        for(int i = 1; i < a.length; i++) {
            ArrayList<Integer> currentSubset = subsets.get(arrayNum);
            
            boolean valid = true;
            for(int num : currentSubset) {
                if(Math.abs(num - a[i]) > 1) {
                    valid = false;
                    break;
                }
            }
            
            if(valid) 
                currentSubset.add(a[i]);
            else {
                arrayNum++;
                ArrayList<Integer> anotherSubset = new ArrayList();
                anotherSubset.add(a[i]);
                subsets.add(anotherSubset);
            }
        }
        
        int max = 0;
        for(ArrayList<Integer> subset : subsets) {
            if(subset.size() > max)
                max = subset.size();
        }
        
        System.out.println(max);
    }
}