using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        "abc\u0000deffff"

            .Where(Char.IsLetterOrDigit)

            .GroupBy(c => c)

            .Aggregate((seed, next) =>

            {

                Console.WriteLine(next.Key + ": " + next.Count());

                return seed;

            });

    }

}