Technion-Israel Institute of Technology, Computer Science Department Haifa, 32000 Israel. sberco@gmail.com|Technion-Israel Institute of Technology, Computer Science Department Haifa, 32000 Israel. sberco@gmail.com|Technion-Israel Institute of Technology, Computer Science Department Haifa, 32000 Israel. sberco@gmail.com|Technion-Israel Institute of Technology, Computer Science Department Haifa, 32000 Israel. sberco@gmail.com