Exam 6. Exam Schedule

namespace _1.ExamSchedule
{
    using System;
    using System.Globalization;
    using System.Threading;

    public class CalculateTimeTheExamEnd
    {
        public static void Main(string[] args)
        {
            Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;
            checked
            {
                string startHour = Console.ReadLine();
                string startMinutes = Console.ReadLine();
                string partOfDay = Console.ReadLine();
                int durationHours = int.Parse(Console.ReadLine());
                int durationMinutes = int.Parse(Console.ReadLine());

                string timeStr = startHour + ':' + startMinutes + ' ' + partOfDay;
                DateTime startTime = DateTime.Parse(timeStr);
                DateTime endTime = startTime.AddHours((double)durationHours);
                endTime = endTime.AddMinutes((double)durationMinutes);

                Console.WriteLine(endTime.ToString("hh:mm:tt"));
            }
        }
    }
}