#include <iostream>

#include <stack>
#include <queue>
#include <deque>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>

#include <cassert>
#include <cmath>
#include <algorithm>
#include <cstdint>

#include <fstream>

#include <cassert>

using namespace std;

#define MY_PI 3.14159265358979323846264338327950288
using LL = long long;
const int INF = 1e9;

const long double kek = 1.0, kek0 = 0.0;
const float eps = 1e-9;
#define DB(x) cerr << #x << " " << x << endl;

int final;
map < int, int > cost;
vector < int > ans (3000000, INF);



int main()
{
	//gen(100);
	//freopen("input.txt", "r", stdin);
	cin.tie(nullptr);
	ios_base::sync_with_stdio(false);
	int n, k;
	int ans = 0;
	vector < int > sum(200, 0);
	cin >> n;
	vector < int > x(n);
	for (int i = 0; i < n; ++i) {
		int a;
		cin >> a;
		a += 10;
		sum[a]++;
		ans = max(ans, max(sum[a] + sum[a - 1], sum[a] + sum[a+1]));
	}
	cout << ans;
	return 0;
}