#include <bits/stdc++.h>
using namespace std;
int main(void){
    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 + 1] - a[i] == 1){
            cout << 2 << endl;
            return 0;
        }
    }
    cout << 1 << endl;
    return 0;
}