public string Test25(int f, int s)
        {
            var first = new OwnBigInteger();

            foreach (var value in f.ToString())
            {
                first.Add(int.Parse(value.ToString()), true);
            }
            first.Print(true);

            var second = new OwnBigInteger();

            foreach (var value in s.ToString())
            {
                second.Add(int.Parse(value.ToString()), true);
            }
            second.Print(true);

            var result = OwnBigInteger.AddInReverseOrder(first, second);

            Console.WriteLine("Result is");
            result.Print(true);
            var test25 = result.ToString();

            return(test25);
        }
        public static OwnBigInteger AddInReverseOrder(
            OwnBigInteger first, OwnBigInteger second)
        {
            var  res          = new OwnBigInteger();
            Node firstRunner  = first._head;
            Node secondRunner = second._head;
            int  carry        = 0;

            while (firstRunner != null && secondRunner != null)
            {
                int i = firstRunner.item + secondRunner.item + carry;
                carry = i >= 10 ? 1 : 0;
                res.Add(i % 10, false);
                firstRunner  = firstRunner.next;
                secondRunner = secondRunner.next;
            }
            if (first._length > second._length)
            {
                while (firstRunner != null)
                {
                    res.Add(firstRunner.item + carry, false);
                    firstRunner = firstRunner.next;
                }
            }
            else
            {
                while (secondRunner != null)
                {
                    res.Add(secondRunner.item + carry, false);
                    secondRunner = secondRunner.next;
                }
            }
            return(res);
        }