#include<stdio.h>
int h[100005], l;
int comp_h(int a, int b)
{
	if (h[a] > h[b])
		return 1;
	else
		return -1;
}
void swap_h(int a, int b)
{
	int f = h[a];
	h[a] = h[b];
	h[b] = f;
	return;
}
void push(int ne)
{
	h[l] = ne;
	int p = l;
	l++;
	for (; p > 0; p = (p - 1) / 2)
		if (comp_h((p - 1) / 2, p) > 0)
			swap_h((p - 1) / 2, p);
	return;
}
int pop()
{
	l--;
	swap_h(0, l);
	int p = 0;
	for (;;)
	{
		if (2 * p + 2 < l)
		{
			if (comp_h(2 * p + 1, 2 * p + 2) > 0)
			{
				if (comp_h(p, 2 * p + 2) > 0)
					swap_h(p, 2 * p + 2);
				p = 2 * p + 2;
			}
			else
			{
				if (comp_h(p, 2 * p + 1) > 0)
					swap_h(p, 2 * p + 1);
				p = 2 * p + 1;
			}
		}
		else if (2 * p + 1 < l)
		{
			if (comp_h(p, 2 * p + 1) > 0)
				swap_h(p, 2 * p + 1);
			p = 2 * p + 1;
		}
		else
			break;
	}
	return h[l];
}
int main()
{
	int n;
	scanf("%d", &n);
	int i;
	int a[100005];
	for (i = 0; i < n; i++)
		scanf("%d", &a[i]);
	l = 0;
	for (i = 0; i < n; i++)
		push(a[i]);
	for (i = 0; i < n; i++)
		a[i] = pop();
	int b[100005], c[100005], d = 1;
	b[0] = a[0];
	c[0] = 1;
	for (i = 1; i < n; i++)
	{
		if (a[i] == b[d - 1])
			c[d - 1]++;
		else
		{
			b[d] = a[i];
			c[d] = 1;
			d++;
		}
	}
	int ans = 0;
	for (i = 0; i < d; i++)
		if (ans < c[i])
			ans = c[i];
	for (i = 0; i < d - 1; i++)
		if (b[i] + 1 == b[i + 1] && ans < c[i] + c[i + 1])
			ans = c[i] + c[i + 1];
	printf("%d\n", ans);
	return 0;
}