public void Test_FrontBackNumerRecursive_2()
        {
            var numTest = new Exercise1();
            var result  = numTest.FrontBackNumbers_Recursive(1234567890);

            Assert.AreEqual(1029384756, result);
        }
        public void Test_FrontBackNumerRecursive_3()
        {
            var numTest = new Exercise1();
            var result  = numTest.FrontBackNumbers_Recursive(123456789);

            Assert.AreEqual(192837465, result);
        }
        public void Test_FrontBackNumerRecursive_1()
        {
            var numTest = new Exercise1();
            var result  = numTest.FrontBackNumbers_Recursive(123456);

            Assert.AreEqual(162534, result);
        }