import java.sql.SQLOutput;
import java.util.Scanner;

public class Calculator {
    public static void main(String[] args) {
        printToScreen("Старт программы", true);
        String numberOne = enterNum();
        String numberTwo = enterNum();
        printToScreen("Принял: ", false);
        printToScreen(numberOne, true);
        printToScreen("Принял: ", false);
        printToScreen(numberTwo, true);
        int firstNum = stringToInteger(numberOne);
        int secondNum = stringToInteger(numberTwo);
        int thirdNum = calcDifference(firstNum, secondNum);
        printToScreen("Результат: ", false);
        printToScreen(String.valueOf(thirdNum), true);
        printToScreen("Конец программы", false);
    }

    public static String enterNum() {
        Scanner scanner = new Scanner(System.in);
        printToScreen("Введите число:", false);
        String number = scanner.nextLine();
        if (checkString(number)) {
            return number;
        } else {
            return enterNum();
        }
    }

    public static int stringToInteger(String stringData) {
        return Integer.parseInt(stringData);
    }

    public static int calcDifference(int firstNumber, int secondNumber) {
        printToScreen("Начинаю считать", true);
        return firstNumber - secondNumber;
    }

    public static void printToScreen(String abraCadaBra, boolean addNewLine) {
        if (addNewLine) {
            System.out.println(abraCadaBra);
        } else {
            System.out.print(abraCadaBra);
        }
    }

    public static boolean checkString(String string) {
        try {
            Integer.parseInt(string);
            return true;
        } catch (IllegalArgumentException e) {
            return false;
        }
    }
}