OnTimeForTheExam

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            int examHour = int.Parse(Console.ReadLine());
            int examMinute = int.Parse(Console.ReadLine());
            int arriveHour = int.Parse(Console.ReadLine());
            int arriveMinute = int.Parse(Console.ReadLine());

            int examTime = examHour * 60 + examMinute;
            int arriveTime = arriveHour * 60 + arriveMinute;

            int timeDiff = examTime - arriveTime;

            string result = string.Empty;
            if (timeDiff == 0)
            {
                result = "On time";
            }
            else if (timeDiff >= 1 && timeDiff <= 30)
            {
                result = $"On time\r\n{timeDiff} minutes before the start";
            }
            else if (timeDiff > 30 && timeDiff < 60)
            {
                result = $"Early\r\n{timeDiff} minutes before the start";
            }
            else if (timeDiff >= 60)
            {
                int hour = timeDiff / 60;
                int minute = timeDiff % 60;

                result = $"Early\r\n{hour}:{minute:d2} hours before the start";
            }
            else if (timeDiff <= -1 && timeDiff >= -59)
            {
                result = $"Late\r\n{Math.Abs(timeDiff)} minutes after the start";
            }
            else if (timeDiff <= -60)
            {
                int hour = Math.Abs(timeDiff / 60);
                int minute = Math.Abs(timeDiff % 60);

                result = $"Late\r\n{hour}:{minute:d2} hours after the start";
            }

            Console.WriteLine(result);
        }
    }
}