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 maxCount = 0;
        int subset[] = new int[n];
        int elemCount;
        for(int i=0; i<n; i++){
            elemCount = -1;
            subset[++elemCount] = a[i];
            for(int j=0; j<n; j++) { //consider each element if its a candidate element in the subset or not
                if(j!=i){ //don't consider the current element itself
                    int k = 0;
                    for(k=0; k<=elemCount; k++) { //check if the candidate element is differ by just 1 from each element
                        if(Math.abs(subset[k]-a[j]) > 1) {
                            break;
                        }                    
                    }
                    if(k>elemCount){
                        subset[++elemCount] = a[j]; //its a candidate element then push it into subset
                    }
                }
            }
            if((elemCount+1)>maxCount){
                maxCount = elemCount + 1;
            }
        }
        System.out.println(maxCount);
    }
}