#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
 
int main() {
	int n;
	cin >> n;
	vector<int> v(n);
	for (int i = 0; i < n; i++)
		cin >> v[i];
	sort(v.begin(), v.end());
	int len = 0, count = 1, first = v[0];
	for (int i = 1; i < v.size(); i++) {
		if (first == v[i] || first + 1 == v[i])
			count++;
		else {
			if (count > len)
				len = count;
			count = 1;
			first = v[i];
		}
	}
	cout << max(len, count) << endl;
	return 0;
}

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