using System;

 using System.Collections.Generic;

 using System.Linq;

 using System.Text;

 using System.Threading.Tasks;

 namespace ConsoleApplication1

 {

     class Program

     {

         static void Main(string[] args)

         {

             Console.WriteLine("请输入第一个加数");

             string oneNum = Console.ReadLine();

             Console.WriteLine("请输入第二个加数");

             string twoNum = Console.ReadLine();

             string result = TwoBigNumAdd(oneNum, twoNum);

             Console.WriteLine(result);

         }

         static string TwoBigNumAdd(string a, string b)

         {

             int k = ;

             List<int> array = new List<int>();

             List<int> one = new List<int>();

             List<int> two = new List<int>();

             //将两个数处理成相同长度的字符串，短的小的数字前面补0

             for (int i = ; i < (a.Length > b.Length ? a.Length : b.Length); i++)

             {

                 if (i >= a.Length)

                     one.Insert(i - a.Length, );

                 else

                     one.Add(int.Parse(a[i].ToString()));

                 if (i >= b.Length)

                     two.Insert(i - b.Length, );

                 else

                     two.Add(int.Parse(b[i].ToString()));

             }

             //array集合用于存储相加的和，所以长度最大也只会比最大的数长度长1，刚开始全部存0

             for (int i = ; i <= (a.Length > b.Length ? a.Length : b.Length); i++)

             {

                 array.Add();

             }

             //从低位往高位每位开始相加，如果相加 >=10 则进1取余

             for (int i = (a.Length > b.Length ? a.Length : b.Length) - ; i >= ; i--)

             {

                 array[i + ] += (one[i] + two[i]) % ;

                 k = (one[i] + two[i]) / ;

                 array[i] += k;

             }

             //如果首位为0，则移除

             if (array[] == )

             {

                 array.RemoveAt();

             }

             //将集合转换成字符串返回

             StringBuilder result = new StringBuilder();

             for (int i = ; i < array.Count; i++)

             {

                 result.Append(array[i]);

             }

             return result.ToString();

         }

     }

 }