using System;

public class Hello
{
    static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        var a = new int[n];
        for (int i = 0; i < n; i++) a[i] = int.Parse(Console.ReadLine().Trim());
        getAns(n, a);
    }
    static void getAns (int n, int[] a)
    {
        Array.Sort(a);
        var count = 0;
        for (int i = 0; i < n-1; i++)
            if (a[i + 1] - a[i] == 1) { Console.WriteLine(2); return; }
        Console.WriteLine(1);
    }
}