#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());

	for (int i = 0; i < N - 1; i++) {
		if (A[i] + 1 == A[i + 1]) {
			cout << 2 << '\n';
			return 0;
		}
	}
	cout << 1 << '\n';
}