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();
        }
        System.out.println(ans(a));
    }
    
    public static int ans(int[] arr) {
        int[] counts = new int[101];
        for (int i = 0; i < arr.length; i++) {
            counts[arr[i]] += 1;
        }
        
        int max_count = 0;
        for (int i = 1; i< counts.length; i++) {
            if (counts[i] + counts[i-1] > max_count) 
                max_count = counts[i] + counts[i-1];
        }
        return max_count;
    }
}