#include <bits/stdc++.h>
using namespace std;

#define endl '\n'
#define ff first
#define ss second
#define mp make_pair
#define pb push_back

typedef long long llong;
typedef pair<int, int> pii;

void solve() {

	int n;
	cin >> n;

	vector<int> cnt(100, 0);

	for (int i = 0; i < n; i++) {

		int val;
		cin >> val;
		cnt[val]++;

	}


	int ans = 0;
	
	for (int i = 1; i < 100; i++) {

		ans = max(ans, cnt[i] + cnt[i - 1]);

	}	

	cout << ans;


}

int main() {

	ios_base::sync_with_stdio(0);
	cin.tie(0);

	#ifdef LOCAL
		ifstream in("in");
		cin.rdbuf(in.rdbuf());
	#endif

	solve();

}