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();
        }

        int[] count = new int[101];
        for(int a_i=0; a_i < n; a_i++){
            count[a[a_i]]++;
        }
        int out = 0;
        for(int a_i=0; a_i < 100; a_i++){
            out = count[a_i] + count[a_i+1] > out ? count[a_i] + count[a_i+1] : out;
        }
        System.out.println("" + out);
  
    }
}