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[101];
        for(int a_i=0; a_i < n; a_i++){
            a[in.nextInt()]++ ;
        }
        int ans = 0;
        for(int i = 1; i <= 100; i++){
          ans = Math.max(ans, a[i]+ a[i-1]);
        }
      System.out.println(ans);
    }
}