#include <iostream>
#include <cstdlib>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
    int n;
    cin >> n;
    
    vector<int> as(n);
    
    for (int& a : as) {
        cin >> a;
    }
    
    sort(as.begin(), as.end());
    
    bool len = false;
    
    for (int i = 0; i < n - 1; i++) {
        if (as[i] + 1 == as[i + 1]) {
            len = true;
        }
    }
    
    cout << (len ? 2 : 1) << endl;
}