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

class Program
{
    static int NN => int.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var a = NList;
        WriteLine(Fruit(n, a));
    }
    static long Fruit(int n, long[] a)
    {
        var set = new HashSet<long>(a);
        foreach (var ai in a) set.Add(ai + 1);
        var sa = a.ToList();
        sa.Sort();
        var dic = new Dictionary<long, long>();
        foreach (var i in sa)
        {
            if (dic.ContainsKey(i - 1))
            {
                dic[i + 1] = dic[i - 1];
            }
            if (dic.ContainsKey(i)) ++dic[i];
            else dic[i] = 1;
        }
        return dic.Sum(kv => kv.Value);
    }
}