using System;

using System.Linq;

using System.Numerics;

​

public class HelloWorld

{

    public static void Main(string[] args)

    {

        byte[] blocks = { 3, 1, 4, 1, 1, 1, 4, 3, 1, 1, 6, 7 };

        Console.WriteLine (CountUniqueBytes(blocks));

    }

    static int CountUniqueBytes(byte[] blocks)

    {

        ulong[] bitmask = blocks

            .Aggregate(new ulong[4], (mask, b) =>

            {

                mask[b / 64] |= 1UL << (b % 64);

                return mask;

            });

​

        return bitmask.Sum(BitOperations.PopCount);

    }

}