C# Character Multiplier

using System;
using System.Linq;
using System.Collections.Generic;
using System.Text;
namespace Task2
{
    class Program
    {
        static void Main(string[] args)
        {



            string[] input = Console.ReadLine().Split(' ').ToArray();


            string str1 = input[0];

            string str2 = input[1];

            int Sum = 0;
            if (str1.Length < str2.Length)
            {
                for (int i = 0; i < str1.Length; i++)
                {
                    int str1Value = str1[i];
                    int str2Value = str2[i];

                    Sum += str1Value * str2Value;
                    if (i == str1.Length - 1)
                    {
                        string difference = str2.Substring(str1.Length);
                        int differenceValue = str2.IndexOf(difference);
                        Sum += differenceValue;

                    }
                }

            }
            if (str1.Length > str2.Length)
            {
                int str1Value = 0;
                int str2Value = 0;
                for (int i = 0; i < str2.Length; i++)
                {
                     str1Value = str1[i];
                     str2Value = str2[i];

                    Sum += str1Value * str2Value;
                    if (i == str2.Length - 1)
                    {
                        string difference = str1.Substring(str2.Length);
                        int differenceValue = str1.IndexOf(difference);
                        Sum += differenceValue;

                    }
                }



            }
            if(str1.Length == str2.Length)
            {
                for (int i = 0; i < str2.Length; i++)
                {
                    int str1Value = str1[i];
                    int str2Value = str2[i];

                    Sum += str1Value * str2Value;



                }
            }

            Console.WriteLine(Sum);
        }
    }
}