Isabel has an interesting way of summing up the values in an array A of n integers, where n is a power of two. She creates an array B of half the size of A and sets B[i] = A[2i]+ A[2i+ 1], for i = 0,1, . . . , (n/2)− 1. If B has size 1, then she outputs B[0]. Otherwise, she replaces A with B, and repeats the process. What is the running time of her algorithm?