ChangeEvenBits.cs

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

class ChangeEvenBits
{
    static void Main()
    {
        int numbers = int.Parse(Console.ReadLine());
        BigInteger[] bits = new BigInteger[numbers];
        for (int i = 0; i < numbers; i++)
        {
            bits[i] = BigInteger.Parse(Console.ReadLine());
        }

        BigInteger L = BigInteger.Parse(Console.ReadLine());
        string stringL = ConvertToBinary(L).PadLeft(64, '0');
        List<char> list = stringL.ToList();

        int replaced = 0;
        for (int k = 0; k < numbers; k++)
        {
            string current = ConvertToBinary(bits[k]);
            list.Reverse();
            int positions = 0;
            for (int p = 0; p < current.Length; p ++)
            {
                if (list[positions] == '0')
                {
                    list[positions] = '1';
                    replaced++;
                }

                positions += 2;
            }
            list.Reverse();

        }
        string result = "";
        foreach (var item in list)
        {
            result += item;
        }
        Print(result);
        Console.WriteLine(replaced);




    }

    private static void Print(string input)
    {
        BigInteger currentNum = BigInteger.Parse(input);
        long sum = 0;
        long sabiratel = 1;
        for (long i = 0; i < input.Length; i++)
        {
            if (currentNum % 10 == 1)
            {
                sum += sabiratel;
            }
            currentNum /= 10;
            sabiratel *= 2;
        }
        Console.WriteLine(sum);
    }

    public static string ConvertToBinary(BigInteger value)
    {
        if (value == 0) return "0";
        System.Text.StringBuilder b = new System.Text.StringBuilder();
        while (value != 0)
        {
            b.Insert(0, ((value & 1) == 1) ? '1' : '0');
            value >>= 1;
        }
        return b.ToString();
    }
}