Couting Diff

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Bai1
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] a = { 3, 4, 5, 1, 7, 10, 2};
            Array.Sort(a);
            List<int> res = new List<int>();

            int i = 1;
            int currentValue = a[0];
            res.Add(currentValue);

            while (i < a.Length )
            {
                while (currentValue == a[i]) i++;
                currentValue = a[i];
                res.Add(currentValue);
                i++;
            }

            Console.WriteLine(res.Count);
        }


    }
}