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(),i;
        int[] a = new int[n];
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
        }
        int f[] = new int[105];
        for(i=0; i<n; i++){
            f[a[i]]++;
        }
        int max=0;
        for(i=1; i<=99; i++){
            if(f[i]+f[i+1] > max)
                max=f[i]+f[i+1];
        }
        System.out.println(max);
    }
}