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 max = 0;
        for(int v = 0; v < 100; ++v) {
            int hits = 0;
            for(int i = 0; i < n; ++i) {
                if(a[i] == v || a[i] == v+1)
                    ++hits;
            }
            if(hits > max)
                max = hits;
        }
        System.out.println(max);
    }
}