import java.util.*;
import java.io.*;

public class SubClassException{

  class Exception extends Exception{

    public static void main(String[] args) {


        Scanner ccnumber = new Scanner(System.in);
        int j = 0;
        int x = 1;


        do {
            System.out.println("Enter your credit card number: ");
            String cardnumber = ccnumber;

            try {
                System.out.println(Long.parseLong(cardnumber));
            } catch (Exception e) {
                System.out.println(e);
            }


        if (cardnumber.length() == 15) {
        try {
            cardnumber.startsWith("3");
            System.out.println("You're Using A American Express Card");
            System.out.println("Enter Security Code: ");
            String secNum = ccnumber;
        } catch (Exception e){
            System.out.println(e);
        }
        break;
    }
    if (cardnumber.length() == 16) {
        try {
            cardnumber.startsWith("6011");
            System.out.println("You're Using A Discover Card");
            System.out.println("Enter Security Code: ");
            String secNum = ccnumber;
        } catch (Exception e) {
            System.out.println(e);
        }
        break;
    }
    if (cardnumber.length() == 16) {
        try {
            cardnumber.startsWith("5");
            System.out.println("You're Using A Mastercard");
            System.out.println("Enter Security Code: ");
            String secNum = ccnumber;
        } catch (Exception e) {
            System.out.println(e);
        }

        break;
    }
    if (cardnumber.length() == 16) {
        try {
            cardnumber.startsWith("4");
            System.out.println("You're Using A Visa Card");
            System.out.println("Enter Security Code: ");
            String secNum = ccnumber;
        } catch (Exception e) {
            System.out.println(e);
        }

        break;
    }
    else {
        try {
            int sum = 0;

            boolean alternate = false;
            for (int i = cardnumber.length() - 1; i >= 0; i--) {
                int n = Integer.parseInt(cardnumber.substring(i, i + 1));
                if (alternate) {
                    n *= 2;
                    if (n > 9) {
                        n = (n % 10) + 1;
                    }
                }
                sum += n;
                alternate = !alternate;
            }
            boolean i = sum % 10 == 0;
            System.out.println(sum);
        } catch (Exception e) {
            System.out.println(e);
        }
    }
        System.out.println("this is not a supported card");
        {  j++; if (j==2)
            System.out.println("Max Tries Reached");
        }
    } while (j==1);



    }
  }
}