using System;

using System.Collections.Generic;

​

public abstract class Person {

    public abstract bool Pass(IVisitorValidator validator);

}

​

public class Child: Person {

    public int Age { get;set;}

    public override bool Pass(IVisitorValidator validator){

        return validator.Validate(this);

    }

}

​

public class Adult: Person {

    public bool IsStudent { get;set;}

    public override bool Pass(IVisitorValidator validator){

        return validator.Validate(this);

    }

}

​

public class Senior: Person{

    public bool IsVeteran { get; set; }

    public override bool Pass(IVisitorValidator validator){

        return validator.Validate(this);

    }

}

​

public abstract class IVisitorValidator {

    public decimal Money {get; set;}

    public int Count {get;set;}

    public abstract bool Validate(Child child);

    public abstract bool Validate(Adult child);

    public abstract bool Validate(Senior child);

    public bool IsValid(Person person){

        // metro card validation logic goes here

        // if metro card is valid then

        return true;

    }

}

​

public class BusVisitorValidator: IVisitorValidator {

    public override bool Validate(Child child){

        if(IsValid(child)){

            Count++;

            if(child.Age > 7) Money +=2;

            return true;

        }

        return false;

    }

    public override bool Validate(Adult adult){

        if(IsValid(adult)){

            Count++;

            Money += adult.IsStudent ? 2 : 2.5M;

            return true;

        }

        return false;

    }

    public override bool Validate(Senior senior){

        if(IsValid(senior)){

            Count++;

            if(!senior.IsVeteran) Money += 2;

            return true;

        }

        return false;

    }

}

​

public class Program

{

    public static void Main()

    {

        var queue = new List<Person>()

        {

            new Child(),

            new Adult(),

            new Adult(){IsStudent = true},

            new Senior(),

            new Senior(){IsVeteran = true}

        };

        var busValidator = new BusVisitorValidator();

        foreach (var person in queue)

        {

            person.Pass(busValidator);

        }

        Console.WriteLine("People: " + busValidator.Count);

        Console.WriteLine("Amount: $" + busValidator.Money);

    }

}