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[] arr = new int[n];
        for(int a_i=0; a_i < n; a_i++){
            arr[a_i] = in.nextInt();
        }
        int ans = 1;
        Arrays.sort(arr);
        int ti = 0, tn = arr[0];
        int curr = 1;
        int temp = 1;
        while (curr < n) {
            if (arr[curr] == tn || arr[curr] == tn+1) {
                temp++;
                curr++;    		
            }
            else {
                ans = Math.max(ans, temp);
                temp = 1;
                while (ti < n && arr[ti] == tn) {
                    ti++;
                }
                tn = arr[ti];
                curr = ti+1;
            }    	
        }
        ans = Math.max(temp, ans);
        System.out.println(ans);
    }
}