C#_DecToBin.cs

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


class DecToBin
{
    static void Main()
    {
        long decNumber = long.Parse(Console.ReadLine());
        string binNumber = "";
        while (decNumber != 0)
        {
            int remain = (int)decNumber % 2;
            decNumber /= 2;
            binNumber = remain + binNumber;
        }
        Console.WriteLine(binNumber);
    }
}