#include <iostream>
#include <algorithm>
#include <vector>
#include <set>

using namespace std;

int main()
{
	int n;
	cin >> n;
	vector<int> a(n);
	for (int i = 0; i < n; ++i)
		cin >> a[i];

	set<int> a_set(a.begin(), a.end());

	int max = 0;

	for (int x : a_set)
	{
		int cnt = count(a.begin(), a.end(), x) + count(a.begin(), a.end(), x + 1);
		max = cnt > max ? cnt : max;
	}

	cout << max << endl;
}