Starting from the number 123456789, at each step, we are swaping two adjacent numbers which are different from zero, and then decreasing the two numbers by 1. What is the sum of digits of the least number that can be get after finite steps?<spanclass=′latex−bold′>(A)</span>0<spanclass=′latex−bold′>(B)</span>1<spanclass=′latex−bold′>(C)</span>3<spanclass=′latex−bold′>(D)</span>5<spanclass=′latex−bold′>(E)</span>9