abstract class ParrotGenerator
    {
        public static Parrot AfricanParrot(int numberOfCoconuts)
        {
            return new AfricanParrot(numberOfCoconuts);
        }

        public static Parrot EuropeanParrot()
        {
            return new EuropeanParrot();
        }

        public static Parrot NorvegianBlueParrot(bool isNailed, double voltage)
        {
            return new NorwegianBlueParrot(isNailed, voltage);
        }
    }

   public abstract class Parrot
    {
        protected const double BaseSpeed = 12.0;

        public abstract double GetSpeed();
    }

 class NorwegianBlueParrot : Parrot
    {
        private readonly bool _isNailed;
        private readonly double _voltage;

        public NorwegianBlueParrot(bool isNailed, double voltage)
        {
            _isNailed = isNailed;
            _voltage = voltage;
        }

        public override double GetSpeed()
        {
            return (_isNailed) ? 0 : GetBaseSpeed(_voltage);
        }

        private double GetBaseSpeed(double voltage)
        {
            return Math.Min(24.0, voltage * BaseSpeed);
        }
    }

 class AfricanParrot : Parrot
    {
        private readonly int _numberOfCoconuts;

        protected const double LoadFactor = 9.0;

        public AfricanParrot(int numberOfCoconuts)
        {
            _numberOfCoconuts = numberOfCoconuts;
        }

        public override double GetSpeed()
        {
            return Math.Max(0, BaseSpeed - LoadFactor * _numberOfCoconuts);
        }
    }

 public abstract class Parrot
    {
        protected const double BaseSpeed = 12.0;

        public abstract double GetSpeed();
    }