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

public class Solution {

    private static int solve(int[] a) {
        int longestPath = 0;        
        for (int i = 0; i < a.length; i++) {
            int path = 1;
            for (int j = i+1; j < a.length; j++) {
                if (Math.abs(a[i] - a[j]) <= 1) {
                    path++;
                } else {
                    break;
                }
            }
            longestPath = Math.max(longestPath, path);
        }
        return longestPath;
    }
    
    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);
        System.out.println(solve(a));
    }
}