using System;

using System.Text;

​

public class ListNode

{

    public int val;

    public long long val;

    public ListNode next;

    public ListNode(int x) { val = x; }

}

​

public class Solution

{

    public ListNode AddTwoNumbers(ListNode l1, ListNode l2)

    {

        int result = CollapseToNumber(l1) + CollapseToNumber(l2);

        return ConvertToList(result);

    }

    public static int CollapseToNumber(ListNode node)

    {

        int result = 0;

        int index = 0;

        ListNode current = node;

        while(current != null)

        {

            result += (int)(current.val * Math.Pow(10, (double)index));

            current = current.next;

            index++;

        }

        return result;

    }

    public static ListNode ConvertToList(int number)

    {

        if(number == 0)

            return new ListNode(0);

        ListNode current = null;

        ListNode root = null;

        while(number > 0)

        {

            int pop = number % 10;

            number = (int)(number / 10);

            ListNode node = new ListNode(pop);

            if(current != null)

                current.next = node;

            if(current == null)

                root = node;

            current = node;

        }

        return root;

    }

}

​

public class Program

{

    public static void Main()

    {

        var a = 9999999991;

        var b = 9;

        Console.WriteLine(a.GetType().FullName);

        Console.WriteLine(a + b);

        return;

        ListNode value1 = Solution.ConvertToList(9);

        ListNode value2 = Solution.ConvertToList(1999999999);

        ListNode answer = new Solution().AddTwoNumbers(value1, value2);

        Console.WriteLine(PrintListNode(value1));

        Console.WriteLine(PrintListNode(value2));       

        Console.WriteLine(PrintListNode(answer));

    }

    public static StringBuilder PrintListNode(ListNode node, StringBuilder msg = null)

    {

        if(msg == null)

            msg = new StringBuilder();

        if(node.next != null)

        {

            PrintListNode(node.next, msg);

            msg.Append(" <- ");

        }

        msg.Append(node.val);

        return msg;

    }

}