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

int main() {
	ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	int N; cin >> N;
	vector<int>A(N);
	for (int i = 0; i < N; i++) {
		cin >> A[i];
	}
	sort(A.begin(), A.end());
	for (int i = 0; i < N - 1; i++) {
		if (A[i] == A[i + 1] - 1) {
			cout << 2 << endl; return 0;
		}
	}
	cout << 1 << endl;
}