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[] b = new int[100];
        for(int a_i=0; a_i < n; a_i++){
            int x = in.nextInt();
            b[x] += 1;
        }
        
        int max = 0;
        int maxn = 0;
        for (int i = 0; i < 99; ++i) {
            if (b[i] + b[i+1] > maxn) {
                max = i;
                maxn = b[i] + b[i+1];
            }
        }
        
        System.out.println(maxn);
    }
}