#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <map>

using namespace std;

int main() {
	using pp = pair<int, int>;

	std::ios::sync_with_stdio(false);
	unsigned N, A[100];
	map<int, int> occur;

	for (unsigned i = 0; i <= 100; i++)
		occur[i] = 0;

	cin >> N;
	for (unsigned i = 0; i < N; i++) {
		cin >> A[i];

		occur[A[i]]++;
	}
	
	unsigned M = 0;
	for (auto el : occur) {
		unsigned key = el.first,
			rep = el.second;

		unsigned left = rep + (key > 0 ? occur[key - 1] : 0),
			right = rep + (key < 100 ? occur[key + 1] : 0);


		rep = left > right ? left : right;

		if (rep > M)
			M = rep;
	}

	cout << M << endl;
	scanf("\n");
	return 0;
}