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