import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {
    
    public static int maxElementsWithAbsDiffLessThanEqualTo1(int[] a) {
        if(a == null || a.length == 0) {
            return 0;
        }
        
        int maxCount = 0;
        SortedSet<Integer> sortedSet = null;
        Set<Integer> visitedElements = new HashSet<>();
        
        for(int i = 0; i < a.length; i++) {
            if(visitedElements.contains(a[i])) {
                continue;
            }
            
            visitedElements.add(a[i]);
            sortedSet = new TreeSet<>();
            sortedSet.add(a[i]);
            int count = 1;
            
            for(int j = 0; j < a.length; j++) {
                if(j == i) {
                    continue;
                }
                
                if(sortedSet.size() == 1 && Math.abs(a[j] - sortedSet.first()) <= 1) {
                    sortedSet.add(a[j]);
                    count++;
                } else if((Math.abs(a[j] - sortedSet.first()) <= 1) && (Math.abs(a[j] - sortedSet.last()) <= 1)) {
                    sortedSet.add(a[j]);
                    count++;
                }
            }
            
            if(count > maxCount) {
                maxCount = count;
            }
        }
        
        return maxCount;
    }

    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 count = maxElementsWithAbsDiffLessThanEqualTo1(a);
        System.out.println(count);
    }
}