using System;
using System.Collections.Generic;
using System.Linq;

public class HumanTimeFormat
{
    [Flags]
    enum TimeItmes { none = 0, seconds = 1, minutes = 2, hours = 4, days = 8, years = 16 }
    private static readonly int year = 60 * 60 * 24 * 365;
    private static readonly int day = 60 * 60 * 24;
    private static readonly int hour = 60 * 60;
    private static readonly int minute = 60;
    private int[] _data = new int[5];
    private TimeItmes _timeItmes;
    HumanTimeFormat(int second)
    {
        while (second >= year)
        {
            second -= year;
            _data[0]++;
            _timeItmes |= TimeItmes.years;
        }
        while (second >= day)
        {
            second -= day;
            _data[1]++;
            _timeItmes |= TimeItmes.days;
        }
        while (second >= hour)
        {
            second -= hour;
            _data[2]++;
            _timeItmes |= TimeItmes.hours;
        }
        while (second >= minute)
        {
            second -= minute;
            _data[3]++;
            _timeItmes |= TimeItmes.minutes;
        }
        if (second > 0)
        {
            _data[4] = second;
            _timeItmes |= TimeItmes.seconds;
        }
    }

    public string ToString()
    {
        if (_timeItmes == TimeItmes.none)
        {
            return "now";
        }
        List<string> components = new();
        if ((_timeItmes & TimeItmes.years) == TimeItmes.years)
        {
            components.Add($"{_data[0]} year{(_data[0] > 1 ? "s" : "")}");
        }
        if ((_timeItmes & TimeItmes.days) == TimeItmes.days)
        {
            components.Add($"{_data[1]} day{(_data[1] > 1 ? "s" : "")}");
        }
        if ((_timeItmes & TimeItmes.hours) == TimeItmes.hours)
        {
            components.Add($"{_data[2]} hour{(_data[2] > 1 ? "s" : "")}");
        }
        if ((_timeItmes & TimeItmes.minutes) == TimeItmes.minutes)
        {
            components.Add($"{_data[3]} minute{(_data[3] > 1 ? "s" : "")}");
        }
        if ((_timeItmes & TimeItmes.seconds) == TimeItmes.seconds)
        {
            components.Add($"{_data[4]} second{(_data[4] > 1 ? "s" : "")}");
        }

        return components.Count switch
        {
            1 => components[0],
            2 => $"{components[0]} and {components[1]}",
            _ => $"{string.Join(", ", components.Take(components.Count - 1))} and {components[^1]}"
        };
    }

    public static string formatDuration(int seconds) => new HumanTimeFormat(seconds).ToString();
}