Sum Big Numbers - String and Text Processing

using System;
using System.Text;

namespace _06SumBigNumbers
{
    class Program
    {
        static void Main(string[] args)
        {
            string num1 = Console.ReadLine().TrimStart('0');
            string num2 = Console.ReadLine().TrimStart('0');

            int onMind = 0;

            StringBuilder result = new StringBuilder();

            if (num1.Length>num2.Length)
            {
                num2 = num2.PadLeft(num1.Length, '0');
            }
            else
            {
                num1 = num1.PadLeft(num2.Length, '0');
            }

            for (int i = num1.Length - 1; i >= 0; i--)
            {
                char currSymbol1 = num1[i];
                char currSymbol2 = num2[i];

                int num1Digit = int.Parse(currSymbol1.ToString());
                int num2Digit = int.Parse(currSymbol2.ToString());

                int sum = num1Digit + num2Digit + onMind;

                int lastDigit = sum % 10;

                result.Append(lastDigit);
                onMind = sum / 10;

            }

            if (onMind > 0)
            {
                result.Append(onMind);
            }

            StringBuilder answer = new StringBuilder();

            for (int i = result.Length - 1; i >= 0; i--)
            {
                char curr = result[i];
                answer.Append(curr);
            }

            Console.WriteLine(answer.ToString());
        }
    }
}