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();
        }
        Arrays.sort(a);
        
        int curr = a[0];
        int max = 1;
        int val = 1;
        for(int i = 1; i < n; i++) {
            if(a[i] == curr || a[i] == curr + 1) {
                val++;
            } else {
                if(val > max) {
                    max = val;
                }
                curr = a[i];
                val = 1;
            }
        }
        if(val > max) {
            System.out.println(val);
        } else {
            System.out.println(max);
        }
    }
}