num1 = 0;
        do {
            isNotCorrect = false;
            System.out.println("Введи число 1");
            try{
                num1 = Integer.parseInt(scan.nextLine());
            } catch(NumberFormatException exception) {
                isNotCorrect = true;
            }
            if ((isNotCorrect) || (num1 < 0)) {
                isNotCorrect = true;
                System.err.println("Гойда, ошибка");
            }
        } while (isNotCorrect);