import java.util.Scanner;

public class CoveringBases {
    private String originalNumber;
    private String newNumber;
    private int originalBase = 10;
    private int newBase;

    public CoveringBases() {
        this.askUser();
        this.checkValidity();
        this.printAll();
    }

    private void askUser() {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter the number base 10 to convert: ");
        originalNumber = input.nextLine();
        System.out.print("Enter the new base: ");
        newBase = input.nextInt();
    }

    private void checkValidity() {
        if (newBase < 2 || 16 < newBase) {
            System.out.println("Not an acceptable base.");
            System.exit(0);
        }
    }

    private void printAll() {
        System.out.print("The number " + originalNumber + " [base 10] = ");
        System.out.print(convertNumber() + " [base " + newBase + "]");
    }

    private String convertNumber() {
        double value = 0;
        double decDigit = 0;
        char chDigit = 0;
        int length = originalNumber.length();

        // loop through each digit of the original number
        for (int power = 0; power < length; power++) {
            // get the digit character (0 - 9, A - Z)
            chDigit = Character.toUpperCase(originalNumber.charAt(length - 1 - power));

            // get the decimal value of the character
            if (Character.isLetter(chDigit)) {
                decDigit = chDigit - 'A' + 10;
            }

            else if (Character.isDigit(chDigit)) {
                decDigit = chDigit - '0';
            }

            else {
                System.out.println("Not a recognized digit.");
                System.exit(1);
            }

            // add this digit's value to the total
            value += decDigit * Math.pow(originalBase, power);
        }

        int D = 1;
        for (; Math.pow(newBase, D) <= value; D++) {
        }
        // use char array to hold the new digits
        char[] newNum = new char[D];

        double pwr;
        for (int i = D - 1; i >= 0; i--) {
            // calculate the digit for this power of newBase
            pwr = Math.pow(newBase, i);
            decDigit = Math.floor(value / pwr);
            value -= decDigit * pwr;

            // store the digit character
            if (decDigit <= 9) {
                newNum[D - 1 - i] = (char) ('0' + (int) decDigit);
            }

            else {
                newNum[D - 1 - i] = (char) ('A' + (int) (decDigit - 10));
            }
        }

        return new String(newNum);
    }

    public static void main(String[] args) {
        new CoveringBases();
    }
}