using System;

class A
{
    public virtual int get_X()
    {
        throw new NotImplementedException();
    }
}

class B : A
{
    public virtual int X
    {
        get
        {
            throw new NotImplementedException();
        }
    }
}

class C : B
{
    public override int get_X() // here
    {
        return base.get_X();
    }
}