import java.util.Scanner;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();

        int[] counts = new int[100];
        while (n-- > 0) {
            counts[in.nextInt()]++;
        }
        
        int max = -1;
        for (int i = 1; i < 100; i++) {
            int count = counts[i-1] + counts[i];
            if (count > max) {
                max = count;
            }
        }
        
        System.out.println(max);
    }
}