Positive integers are written into squares of a infinite chessboard such that a number n is written n times. If the absolute differences of numbers written into any two squares having a common side is not greater than k, what is the least possible value of k?<spanclass=′latex−bold′>(A)</span>1<spanclass=′latex−bold′>(B)</span>2<spanclass=′latex−bold′>(C)</span>3<spanclass=′latex−bold′>(D)</span>4<spanclass=′latex−bold′>(E)</span>None of the preceding