using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    static long[] LList(long n) => Enumerable.Repeat(0, (int)n).Select(_ => long.Parse(ReadLine())).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var a = LList(n);
        Array.Sort(a);
        var flg = true;
        for (var i = 0; i + 1 < n; ++i)
        {
            if (a[i] + 1 == a[i + 1]) flg = false;
        }
        WriteLine(flg ? 1 : 2);
    }
}