import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {
    static int solve(int n, int a[]) {
        Arrays.sort(a);
        int bestResult = 0;
        for (int i = 0; i < a.length - 1; ++i) {
            int result = 1;
            for (int j = i + 1; j < a.length; ++j) {
                if (Math.abs(a[j] - a[i]) <= 1)
                    ++result;
                else
                    break;
            }
            bestResult = Math.max(bestResult, result);
        }
        return bestResult;
    }

    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();
        }
        System.out.println(solve(n, a));
    }
}