Comparisson and sums of the bigger numbers

using System;
using System.Collections.Generic;
using System.Numerics;

namespace SoftuniExercisesWithVariables
{
    class Program
    {
        static int CalculateSum(int num)
        {
            int tempNum;
            int sum = 0;
            while(num > 0)
            {
                tempNum = num % 10;
                num = num / 10;
                sum += tempNum;
            }
            return sum;
        }

        static void Main(string[] args)
        {
            Console.WriteLine("Enter the number of comparissons you are about to make: ");
            int lines = int.Parse(Console.ReadLine());
            List<int> listNums = new List<int>();
            while(lines > 0)
            {
                string line = Console.ReadLine();
                string[] numbers = line.Split(" ");
                int numberOne = int.Parse(numbers[0]);
                int numberTwo = int.Parse(numbers[1]);
                if(numberOne > numberTwo)
                {
                    listNums.Add(CalculateSum(numberOne));
                }
                else
                {
                    listNums.Add(CalculateSum(numberTwo));
                }
                lines--;
            }
            foreach(int a in listNums)
            {
                Console.WriteLine(a);
            }


        }
    }
}