Exam 3. The Explorer

namespace _3.TheExplorer
{
    using System;

    public class TheExplorer
    {
        public static void Main(string[] args)
        {
            checked
            {
                int numN = int.Parse(Console.ReadLine());
                string hyphenSequenceTopAndBottom = new string('-', numN / 2);
                string hyphenSequenceOnMiddleRow = new string('-', numN - 2);

                // Print Top row:
                Console.WriteLine("{0}{1}{0}", hyphenSequenceTopAndBottom, '*');

                // Print rows betweens Top and Bottom rows:
                for (int row = 1; row < numN - 1; row++)
                {
                    if (row == numN / 2)
                    {
                        Console.WriteLine("{0}{1}{0}", '*', hyphenSequenceOnMiddleRow);
                    }
                    else
                    {
                        // Calculating lenght of Internal hyphen sequences:
                        int lenghtInternalHyphenSequence;
                        if (row < numN / 2)
                        {
                            lenghtInternalHyphenSequence = (row * 2) - 1;
                        }
                        else
                        {
                            lenghtInternalHyphenSequence = ((numN - row - 1) * 2) - 1;
                        }

                        // Create Internal hyphen sequence:
                        string internalHyphenSequence = new string('-', lenghtInternalHyphenSequence);

                        // Calculating and create External hyphen sequence:
                        int lenghtExternalHyphenSequence = (numN - 2 - lenghtInternalHyphenSequence) / 2;
                        string externalHyphenSequence = new string('-', lenghtExternalHyphenSequence);

                        // Print current row:
                        Console.WriteLine("{0}{1}{2}{1}{0}", externalHyphenSequence, '*', internalHyphenSequence);
                    }
                }

                // Print Bottom row:
                Console.WriteLine("{0}{1}{0}", hyphenSequenceTopAndBottom, '*');
            }
        }
    }
}