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 ans = 0;
        Arrays.sort(a);
        int[] x = new int[101];
        for (int i = 0; i < n; i++) {
            x[a[i]]++;
        }
        for (int i = 0; i < 98; i++) {
            if ((x[i]+x[i+1])>ans) {
                ans = x[i]+x[i+1];
            }
        }
        System.out.println(ans);
    }
}