using System;

​

interface INext

{

    int Next();

}

​

abstract class Sequence : INext

{

    protected int currentValue;

    protected int step;

​

    public Sequence(int startValue, int step)

    {

        this.currentValue = startValue;

        this.step = step;

    }

​

    public abstract int Next();

}

​

class ArithmeticSequence : Sequence

{

    public ArithmeticSequence(int startValue, int step) 

    : base(startValue, step) { }

​

    public override int Next()

    {

        int nextValue = currentValue + step;

        currentValue = nextValue;

        return nextValue;

    }

}

​

class GeometricSequence : Sequence

{

    public GeometricSequence(int startValue, int step)

    : base(startValue, step) { }

​

    public override int Next()

    {

        int nextValue = currentValue * step;

        currentValue = nextValue;

        return nextValue;

    }

}

​

class FibonacciSequence : Sequence

{

    private int previousValue;

​

    public FibonacciSequence(int startValue) : base(startValue, 0)

    {

        this.previousValue = startValue;

    }

​

    public override int Next()

    {

        int nextValue = currentValue + previousValue;

        previousValue = currentValue;

        currentValue = nextValue;

        return nextValue;

    }

}

​

public class Program

{

    static void Main()

    {

    Show(new ArithmeticSequence(2, 3));

    Show(new ArithmeticSequence(5, 2));

    Show(new GeometricSequence(2, 2));

    Show(new GeometricSequence(3, 3));

    Show(new FibonacciSequence(1));

    }

​

    static void Show(INext sequence)

{

    for (int i = 0; i < 10; i++)

    {

        Console.Write(sequence.Next() + " ");

    }

​

    Console.WriteLine();

}

}