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) throws NumberFormatException, IOException {
		// TODO Auto-generated method stub
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int n = Integer.parseInt(br.readLine());
		String[] input = br.readLine().split(" ");
		int[] a = new int[n];
		
		for(int i = 0 ; i < a.length ; i++){
			a[i] = Integer.parseInt(input[i]);
		}
		
		Arrays.sort(a);
		int maxCount = 1;
		
		for(int i = 0 ; i < a.length -1 ; i++){
			int tempCount = 1;
			for(int j = i+1 ; j < a.length ; j++){
				if(a[j] == a[i] || a[j] == a[i] + 1 || a[j] == a[i] - 1){
					tempCount++;
				} else {
					break;
				}
			}
			maxCount = Math.max(maxCount, tempCount);
		}

		System.out.println(maxCount);
		
	}
}