#include <iostream>
#include <vector>
#include <algorithm>
#include <cassert>
using namespace std;
using ll = long long;

int main() {
	int N;
	cin >> N;
	assert(1 <= N && N <= 100000);
	vector<int> A(N);
	for (int i = 0; i < N; i++) {
		cin >> A[i];
		assert(1 <= A[i] && A[i] <= 1000000000);
		if (i) assert(A[i - 1] != A[i]);
	}
	sort(A.begin(), A.end());

	vector<int> v(1, A[0]), w(0);
	for (int i = 1; i < N; i++) {
		if (v.back() + 1 < A[i]) v.emplace_back(A[i]);
		else {
			assert(w.empty() || w.back() + 1 < A[i]);
			w.emplace_back(A[i]);
		}
	}

	cout << 2 - w.empty() << '\n';
}