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

using namespace std;

int main() {
	int n;
	cin >> n;
	vector<int> a(n);
	for (int i = 0; i < n; ++i) {
		cin >> a[i];
	}
	sort(a.begin(), a.end());
	int result = 1;
	for (int i = 1; i < n; ++i) {
		int diff = a[i] - a[i - 1];
		if (diff == 1) {
			result = 2;
		}
	}
	cout << result << endl;
	return 0;
}