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();
		}

		Arrays.sort(a);
		int count = 1;
		for (int i = 0; i < a.length; i++) {
			int tempCount = 1;
			for (int j = i + 1; j < a.length; j++) {
				if (a[j] - a[i] > 1) {
					break;
				} else {
					tempCount++;
				}
			}

			if (tempCount > count) {
				count = tempCount;
			}

		}

		System.out.println(count);
	}
}