using System;

public class Program

{

    public static void Main()

    {

        start1:

        Console.WriteLine("Enter your age : ");

        int age = Convert.ToInt16(Console.ReadLine());

        if (age <= 0)

        {

            Console.WriteLine("Please enter a valid age.");

            goto start1;

        }

        start2:     

        Console.WriteLine("Enter number of stations : ");

        double stations = Convert.ToDouble(Console.ReadLine());

        if (stations <= 0 || stations > 30)

        {

            Console.WriteLine("Number of stations is invalid.Please try again.");

            goto start2;

        }

        double children = 0.35;

        double student = 0.50;

        double adult = 0.80;

        double senior = 0.50;

        if ( age <=10)

        {

            Console.WriteLine("Total cost(Children Fare) :$ " + (children * stations));

        }

        else if (age >=11 && age <=21)

        {

            Console.WriteLine("Total cost(Student Fare) :$ " + (student * stations));

        }

        else if (age >= 22 && age <= 55)

        {

            Console.WriteLine("Total cost(Adult Fare) :$ " + (adult * stations));

        }

        else if (age >= 56)

        {

            Console.WriteLine("Total cost(Senior Fare) :$ " + (senior * stations));

        }

    }

}