#define _CRT_SECURE_NO_WARNINGS
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>
int *a, n;

int match_max = 0;
int find_largest_count(int val, int count, int sel, int match)
{
	if (sel == n)
	{
		if (match_max<match)
			match_max = match;
	}
	else
	{
		if (match_max < match)
			match_max = match;
		if (count == 0)
		{
			find_largest_count(a[count], count + 1, sel + 1, 1);
		}
		else
		{
			find_largest_count(val, count + 1, sel + 1, match);
			if (count > 0)
			{
				if (a[count] - val <= 1 && val - a[count] <= 1)
				{
					find_largest_count(a[count], count + 1, sel + 1, match + 1);
				}
			}
		}
	}
	return 0;
}
int main() {

	scanf("%d", &n);
	a = (int *)malloc(sizeof(int) * n);
	for (int a_i = 0; a_i < n; a_i++) {
		scanf("%d", &a[a_i]);
	}
	int i, j;
	for (i = 0; i<n-1; i++)
	{
		for (j = i+1; j<n; j++)
		{
			if (a[i] > a[j])
			{
				int temp = a[i];
				a[i] = a[j];
				a[j] = temp;
			}
		}
	} 
	int cnt;
	for (i = 0; i < n - 1; i++)
	{
		cnt = 1;
		for (j = i + 1; j < n; j++)
		{
			if (a[j] - a[i] <= 1)
				cnt++;
			else
				break;
		}
		if (cnt > match_max)
			match_max = cnt;
	}
	//find_largest_count(0, 0, 0,1);
	printf("%d\n", match_max);
	return 0;
}