import java.util.*;
import java.io.*;
import java.math.*;
import java.util.stream.Stream;

public class Main{
    static  PrintWriter output;
    static  Scanner sc;
    static int cnt ;
    static void solve() {
        int n = sc.nextInt();
        int [] cup = new int[n];
        for(int i=0;i<n;i++) cup[i] = sc.nextInt();
        Arrays.sort(cup);
        int ans = 1;
        for(int i=0;i<n;i++) {
            if(cup[i] + 1 < cup[i+1]) {
                ans = 2;
            }
        }
        output.print(ans);
    }

    public static void main(String[] args) throws IOException{
        output = new PrintWriter(System.out);
        sc = new Scanner(System.in);
        solve();
        output.flush();
    }
}