C# code to convert given whole numbers of seconds to hh:mm:ss

SecondsToTime.cs

using System;

public class SecondsToTime {
    
    public static int Main() {

        double totalSeconds;
        
        Console.Write("Please enter the number of seconds: ");
        string userInput = Console.ReadLine();    
        
        while (!double.TryParse(userInput, out totalSeconds)) {
            if (userInput.Equals("quit")) {
                Console.WriteLine("Exiting the programme.");
                Environment.Exit(0);
            } else {
                Console.WriteLine("Invalid Input. Please enter a whole number");
                userInput = Console.ReadLine();
            }
        }

        TimeSpan t = TimeSpan.FromSeconds(totalSeconds);
        string time = t.ToString(@"hh\h\:mm\m\:ss\s");
        Console.Write(totalSeconds + " seconds = " + time);
        
        return 0;
    }
}