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];
        int arr[] = new int[101];
        for(int i=0; i < n; i++){
            a[i] = in.nextInt();
            arr[a[i]]++;
        }
        
        int max = -1;
        for (int i=1;i<=100;i++){
            int sum  = arr[i] +arr[i-1];
            if (sum > max){
                max = sum;
            }
        }
        
        System.out.println(max);
        
        
    }
}