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[] counts = new int[101];
        for(int a_i=0; a_i < n; a_i++){
            counts[in.nextInt()]++;
        }
        
        int best = counts[0] + counts[1];
        for (int i = 1; i < 100; i++) {
            int c = counts[i] + counts[i+1];
            if (c > best)
                best = c;
        }
        
        System.out.println(best);
        
        
    }
}