reverseTableMultiplication

import java.util.Scanner;

 class ReverseMultiplicationTable {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        String numberString = input.nextLine();

                if (numberString.length() == 3 && !numberString.contains("-") && !numberString.contains("0")) {

            char digit3 = numberString.charAt(0);
            char digit2 = numberString.charAt(1);
            char digit1 = numberString.charAt(2);


            for (int i = 1; i <= Integer.parseInt(String.valueOf(digit3)); i++) {
                for (int j = 1; j <= Integer.parseInt(String.valueOf(digit2)); j++) {
                    for (int k = 1; k <= Integer.parseInt(String.valueOf(digit1)); k++) {
                        int product = i * j * k;
                        System.out.println(i + " * " + j + " * " + k + " = " + product);
                    }
                }
            }
        } else {
            System.out.println("invalid input number!");
        }
    }
}