public void two_elements_array()
        {
            var A = new[] {1, 2000};

            TapeEqulibrium.solution(A).Should().Be(1999);
        }
        public void two_elements_array_2()
        {
            var A = new[] { 1000, -1000 };

            TapeEqulibrium.solution(A).Should().Be(2000);
        }
        public void example()
        {
            var A = new[] {2, 3, 1, 5};

            PermMissingElem.solution(A).Should().Be(4);
        }