#include <iostream>
#include <numeric>
#include <vector>
#include <set>
#include <algorithm>

using namespace std;

template <class T> ostream& operator<<(ostream& o, vector<T>& v)
{ o << '['; for (int i = 0; i < v.size(); i++) o << (i > 0 ? ", " : "") << v[i]; o << ']'; return o; }

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());
    for (int i = 1; i < v.size(); i++) {
        if (v[i-1]+1 == v[i]) {
            cout << 2 << endl;
            return 0;
        }
    }
    cout << 1 << endl;
}