nakov matching

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication4
{
    class Program
    {
        static void Main(string[] args)
        {
            string aInput = Console.ReadLine();
            string bInput = Console.ReadLine();
            string aFirstPart = string.Empty;
            string aSecondPart = string.Empty;
            string bFirstPart = string.Empty;
            string bSecondPart = string.Empty;
            int acounter = 1;
            int bcounter = 1;
            int d = int.Parse(Console.ReadLine());
            int matches = 0;
            for (int i = 0; i < aInput.Length - 1; i++)
            {


                aFirstPart += aInput[i];
                int afirstPartSum = 0;
                foreach (var letter in aFirstPart)
                {
                    afirstPartSum += (int)letter;
                }
                aSecondPart = aInput.Substring(i + 1);
                int asecondPartSum = 0;
                foreach (var letter in aSecondPart)
                {
                    asecondPartSum += (int)letter;
                }
                acounter++;
                for (int j = 0; j < bInput.Length - 1; j++)
                {
                    bFirstPart += bInput[j];
                    int bfirstPartSum = 0;
                    foreach (var letter in bFirstPart)
                    {
                        bfirstPartSum += (int)letter;
                    }
                    bSecondPart = bInput.Substring(j + 1);
                    int bsecondSum = 0;
                    foreach (var letter in bSecondPart)
                    {
                        bsecondSum += (int)letter;
                    }
                    bcounter++;
                    int sum = (int)(Math.Abs((afirstPartSum * bsecondSum) - (bfirstPartSum * asecondPartSum)));
                    if (sum <= d)
                    {
                        Console.WriteLine("({0}|{1}) matches ({2}|{3}) by {4} nakovs", aFirstPart,aSecondPart,bFirstPart,bSecondPart,sum);
                        matches++;
                    }



                }
                bFirstPart = string.Empty;
                bSecondPart = string.Empty;

            }
            if (matches == 0)
            {
                Console.WriteLine("No");
            }
        }
    }
}