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];
        int[] b = new int[101];

        for(int a_i=0; a_i < n; a_i++){
            int x = in.nextInt();
            a[a_i] = x;
            b[x]+=1;
        }
        int maxSum=0;
        for (int i=0;i<100;i++) {
            int tempSum=b[i]+b[i+1];
            if (tempSum>maxSum) {
                maxSum=tempSum;
                      //  System.out.println(i+" "+maxSum);

            }
        }
        System.out.println(maxSum);
    }
}