Exam 4. Crossing Sequences

namespace _4.CrossingSequences
{
    using System;
    using System.Collections.Generic;

    public class CrossingSequences
    {
        private const int MAX = 1000000;

        public static void Main(string[] args)
        {
            checked
            {
                int tribNum1 = int.Parse(Console.ReadLine());
                int tribNum2 = int.Parse(Console.ReadLine());
                int tribNum3 = int.Parse(Console.ReadLine());
                int spiralNum = int.Parse(Console.ReadLine());
                int step = int.Parse(Console.ReadLine());

                if (tribNum1 != spiralNum && tribNum2 != spiralNum && tribNum3 != spiralNum)
                {
                    List<int> seqTribonacci = CalculateTribonacciSequenceAndCreateList(tribNum1, tribNum2, tribNum3);

                    bool foundCrossedNum = false;
                    int counter = 1;
                    while (spiralNum <= MAX)
                    {
                        if (seqTribonacci.Contains(spiralNum))
                        {
                            foundCrossedNum = true;
                            Console.WriteLine(spiralNum);
                            break;
                        }

                        spiralNum += step * (counter / 2);
                        counter++;
                    }

                    if (!foundCrossedNum)
                    {
                        Console.WriteLine("No");
                    }
                }
                else
                {
                    Console.WriteLine(spiralNum);
                }
            }
        }

        private static List<int> CalculateTribonacciSequenceAndCreateList(int tribNum1, int tribNum2, int tribNum3)
        {
            checked
            {
                List<int> numbers = new List<int>(MAX) { tribNum1, tribNum2, tribNum3 };
                int sum = 0;
                do
                {
                    sum = tribNum1 + tribNum2 + tribNum3;
                    if (sum <= MAX)
                    {
                        numbers.Add(sum);
                    }

                    tribNum1 = tribNum2;
                    tribNum2 = tribNum3;
                    tribNum3 = sum;
                }
                while (sum < MAX);

                return numbers;
            }
        }
    }
}