public class Time2
    {
        private int hour;
        private int minute;
        private int second;

        public Time2(int hour = 0, int minute = 0, int second = 0)
        {
            SetTime(hour, minute, second);
        }
        public Time2(Time2 t) :
            this(t.Hour, t.Minute, t.Second)
        {
        }
        public void SetTime(int hour, int minute, int second)
        {
            Hour = hour;
            Minute = minute;
            Second = second;
        }
        public Time2 Next(int hour = 0, int minute = 0, int second = 0)
        {
            int seconds = (Hour + hour) * 3600 + (Minute + minute) * 60 + Second + second;
            Time2 newTime = new Time2();
            newTime.Hour = (seconds / 3600) % 24;
            newTime.Minute = (seconds % 3600) / 60;
            newTime.Second = seconds % 60;
            return newTime;
        }
        public int Hour
        {
            get
            {
                return hour;
            }
            set
            {
                if (value < 0 || value > 23)
                {
                    throw new ArgumentOutOfRangeException(nameof(value), value,
                        $"{nameof(Hour)} must be 0 - 23");
                }
                hour = value;
            }
        }
        public int Minute
        {
            get
            {
                return minute;
            }
            set
            {
                if (value < 0 || value > 59)
                {
                    throw new ArgumentOutOfRangeException(nameof(value), value,
                        $"{nameof(Minute)} must be 0 - 59");
                }
                minute = value;
            }
        }
        public int Second
        {
            get
            {
                return second;
            }
            set
            {
                if (value < 0 || value > 59)
                {
                    throw new ArgumentOutOfRangeException(nameof(value), value,
                        $"{nameof(Second)} must be 0 - 59");
                }
                second = value;
            }
        }
        public string ToUniversalString() =>
            $"{Hour:D2}:{Minute:D2}:{Second:D2}";
        public override string ToString() =>
            $"{((Hour == 0 || Hour == 12) ? 12 : Hour % 12)}:" +
            $"{Minute:D2}:{Second:D2} {(Hour < 12 ? "AM" : "PM")}";
    }
    class Ex4 : Object
    {
        public static void Main()
        {
            var t1 = new Time2();
            var t2 = new Time2(2);
            var t3 = new Time2(21, 34);
            var t4 = new Time2(12, 25, 42);
            var t5 = new Time2(t4);
            t5.Hour = 15;
            var t6 = t5.Next(10, 40, 0);
            Console.WriteLine("t1:");
            Console.WriteLine($"{t1.ToUniversalString()}");
            Console.WriteLine($"{t1.ToString()}\n");
            Console.WriteLine("t2:");
            Console.WriteLine($"{t2.ToUniversalString()}");
            Console.WriteLine($"{t2.ToString()}\n");
            Console.WriteLine("t3:");
            Console.WriteLine($"{t3.ToUniversalString()}");
            Console.WriteLine($"{t3.ToString()}\n");
            Console.WriteLine("t4:");
            Console.WriteLine($"{t4.ToUniversalString()}");
            Console.WriteLine($"{t4.ToString()}\n");
            Console.WriteLine("t5:");
            Console.WriteLine($"{t5.ToUniversalString()}");
            Console.WriteLine($"{t5.ToString()}\n");
            Console.WriteLine("t6:");
            Console.WriteLine($"{t6.ToUniversalString()}");
            Console.WriteLine($"{t6.ToString()}\n");
        }
    }